I can confirm that First Class is no longer in use on the Waterloo to Reading route. It was officially withdrawn in preparation for the Class 701 suburban roll-out, with the 458/5 conversion seeing the First Class removed on those too. It’s only the continued use of 450s on the line due to the 701’s delay that is seeing physical First Class appear, but there has been no change to the withdrawal of First Class as a product from the ‘Windsor side’ services. I agree the timetables could make this clearer though, as routes with First Class tend to denote these services by way of a small ‘1’ symbol or, such as the mainline timetables, text to the effect of ‘First Class is available on services shown in bold’. A simpler and more uniform ‘1’ symbol for services with First Class and blank for services without would be something I’d perhaps have opted for if it was me doing them.
A mixed route example is the Aldershot to Ascot timetable, which on weekday peaks has some through London services that join the Reading route at Ascot. The shuttles are denoted with ‘1’ symbols but the through London trains are shown as Standard Class only. Eg 0619/49 Farnham to Waterloo on Page 5 of
https://www.southwesternrailway.com/plan-my-journey/-/media/35721d50afb94b91afa6c567327aaef9.ashx
Another mixed example is the Portsmouth Direct, which has a random Class 458 working on the 2145 Waterloo to Haslemere, with the timetable showing an ‘S’ for standard class only at
https://www.southwesternrailway.com/plan-my-journey/-/media/b6afddf8dbbe43a28d9895f2ea4121c4.ashx
A copy of the original announcement can be found at:
https://www.surreyheathconservatives.org.uk/news/update-south-western-railway-rail-services