I don't follow, apologies.
The timetable posted by OP suggests that the current slow stopping through service to T5 will switch to T4 - meaning no more slow through service to T5 until December 2019. It's a minor issue for commuters really as it just adds 5/10 minutes on to a journey to T5, ho-hum.
I guess TfL thought T4 (9.5 million passengers p/a) was a better choice than T5 (32 million passengers p/a).
My understanding of the *current* pre TfL Rail situation is this (from the published timetables)
- 2 tph stopping Paddington - T23 (Heathrow Connect) [in reality these trains reach T5 - see comment below]
- 4 tph HEX Paddington - T5 (express)
- shuttle T23 to T4
Post TfL Rail the situation is
- 2 tph stopping Paddington - T4 (TfL Rail) (Should rise to 4 tph if signalling issues are resolved)
- 4 tph HEX Paddington - T5 (express)
- 2 tph T23 to T4
Having looked at Realtimetrains I see that Heathrow Connect trains do reach T5 despite all the public timetables denying this. What a bizarre situation. I can now understand your (and others) comments about T5 slow trains.
Post Dec 2019 the service should be
- 2 tph Abbey Wood - T4 (Crossrail)
- 2 tph Abbey Wood - T5 (Crossrail)
- 4 tph Paddington mainline - T5 (HEX)
Possible T23 - T4 shuttle (not sure about this)
There will also be a study about adding a further 2 tph on Crossrail into Terminal 5.
I don't understand your remark about TfL's "better choice". The Crossrail Act did not envisage Crossrail services to Terminal 5. The plan and scheme scope was always about serving T23 and T4. Serving Terminal 5 was something that had to be negotiated and we know how troublesome that became as HAL tried so hard to extract high track access charges from TfL. Thankfully the respective parties have seemingly reached an agreement that allows Crossrail to reach T5 (better for passengers, meets political aspirations and probably better for the airport) from Dec 2019.