Only in respect of (I think) the slightly unusual (in practice) scenario of arriving inbound in CE and transiting to WT or WTP longhaul. In such circumstances, you're right; per 'the manual' the BA passenger should still be afforded lounge access prior to the longer sector.

Prospero's assertion that the basic premise seems to be the most substantial part of the journey guides the transit access is broadly correct - though CE > WT/WTP would be apparently be an exception.

Are there any others?