the 01:00 from exeter is most likely the sleeper and doesnt really have a fixed route from Taunton it can go via Westbury or Bristol to Swindon/Reading.
I have never been on it via Bristol has anyone here? the only time i did it it went via Westbury & Melksham to Swindon before proceding to Reading.
I've often been on the Sleeper and gone via Bristol
TM‡, I've know passengers to board at Bristol rather than wait till the 04.xx train.
But then it doesn't always go via Bristol, it has a wide range of variations of route between Taunton & Reading., even more on a Sunday night between Exeter St D & Reading.