Maidenhead has an acknowledged capacity problem (that will only get worse when another 10,000 homes are built in the next decade) and therefore curtailing a popular peak service such as the 7.07 so that it doesn't 'hold up the mains' fails to acknowledge that there were actual people expecting that train to arrive and take them to Paddington. A delayed arrival at Paddington for the 7.07 and the 2 trains behind it that are caught in that 12min window is not, in my opinion, as important as people arriving at the station and having no service to take them at all, particularly as it still found time to stop at Reading which has a wide range of fast services.
I can see the logic, and I can see your point about sacrificing the Reading stop rather than the Maidenhead one, but in terms of just delaying the next two trains, I'm afraid it's far from that simple.
Between Ruscombe to Taplow that train recovered five minutes this morning, so that's approximately the 'cost of the stop' in terms of time. Doesn't sound much, does it? But it's not just the one, two or three trains that might have caught it up running behind, it's the concertina affect that can have further back - a bit like when a motorist touches the brakes on the M25 that resulting in a log-jam a few minutes later a junction or two back.
Then there's the feeding points to the main lines to consider, so at Maidenhead East, Slough West, Dolphin Junction and Airport Junction there are all possible conflicts with trains coming off the relief lines to the mains. If they have to wait five minutes they can knock on trains behind them, or possibly trains heading on the relief line in the other direction when they do get to cross over. If they get the signal ahead of the 07:07 then that can lose much more time very quickly as it catches up with them.
Then there's the flighting of platforms at Paddington to consider - everything arrives and departs on a sequence, so an extra delay to an arrival can mean a delayed departure to other services. Or if bad enough the next working of that train can be delayed, which can affect other arrivals and departures, even if, like that one, the train only goes to North Pole Depot after arrival.
The new timetable is tighter than ever in that regard, hence my comment about brutal decisions being more likely. Saving five or so minutes on a critical part of the route can save knock on delays reaching the hundreds of minutes surprisingly easily. I do get understand all that is not the passengers problem, but hopefully that explains a little more why a decision such as this morning's is taken in the wider interest?
If the 7.07 becomes a victim of frequent curtailment then what will likely happen is that myself and my fellow passengers will cease to 'expect' it to arrive and will therefore squash on to the 7.02, negating any benefit of the upgrade in formation.
That train is certainly more fragile than it was and is likely to be more susceptible to problems. That's basically down to it now running as a 5-car from Worcester and getting another 5-cars attached at Oxford, rather than running as a 9-car throughout. Previously it had five minutes booked at Oxford, and if on time usually arrived a couple of minutes early, so there was a bit of leeway should it be running a few minutes late. That booked time at Oxford is now seven minutes, but with the coupling procedure that time is instantly eaten up - indeed this morning it lost a couple more minutes. Expect that operation to get a little slicker over time, but this is the first time
IET▸ 's have coupled at Oxford, and the first time for a lot of drivers that they have coupled up in service ever. More time is ideally needed. It then has two minutes less to get to Maidenhead which was slack in the old
HST▸ based schedule, but again that gave it a little more scope to make back a few minutes worth of delay.
We will see whether it becomes one of the genuine problem trains that action has to be taken over when a little more data on it is received, but like I say, I fear it will be far less reliable - initially at least - than the old incarnation of it.
It is also worth noting that Maidenhead used to have the 7.10 (slough and paddington only) that used to catch anyone who really wanted a seat or whose train had been curtailed but this has now been removed. That means that the capacity in that super-peak window of 6.45-7.15 has shrunk from 23 carriages to 20, and this morning was only 12.
The 07:10 was principally designed to be a commuter train for the good people of Slough, rather than Maidenhead. It hasn't been removed, it just runs 5 minutes later from Maidenhead (arriving 4 minutes later at Paddington). It's the 07:18 that's been removed from Maidenhead which no doubt is the reason behind the extra passengers for the two earlier trains. I wonder how the following 07:32 now loads?
The capacity in the the 'super-peak' 06:45-07:15 window you describe is now:
06:45 - 9-car IET
07:02 - 12-car 387
07:07 - 10-car IET
07:15 - 8-car 387
Total: 39 carriages, but down to 29 today.
Stretching that window slightly, it used to be:
06:42 - 5-car IET
07:01 - 5-car IET
07:08 - 8-car IET
07:10 - 8-car 387
07:18 - 8-car 387
Total: 34 carriages.
I can see how the 07:07 is a big loss, but it's nowhere near the shrinkage you describe, and is an increase when everything goes to plan. Fingers crossed for tomorrow!