On line vendors and ticket machines are under no such obligation. In a town near here, the TVM▸ has [had - not checked for a few months] Peak and Offpeak to London, and travelcards for the same times and a couple of others on the front "London" screen. Even late in the day when all remaining London trains are super off peak. There is a button "look at other alternative fares" which finds the superoffpeak for those in the know.
Just checked ... bought a super off peak ticket. Standard and Off Peak fares on front screen; had to go through 2 other screens to find super off peak. Aren't all trains super off peak today?