How bizarre, I know some airlines cabin crew can ad lib a bit of the briefings/announcements - South West are renowned for it, equally as someone already mentioned AA currently have the 'mask' sentence and refer to cabin crew as captains representative. I've rarely heard any BA crew go far off script and certainly never a 'school teacher' lecture like this, very odd.
As for 2nd meal, that's inexcusable really, they can manage it on East Coast flights no issue and while the A350 galley arrangement may be inadequate, I've been on A350s and got a 2nd meal numerous times with BA....indeed even IB managed it last week on a 6 hour JFK to MAD.
This can only really come down to a crew decision not to do it.