> Do they honestly expect they're never going to have to give a speech defending something they disagreed with, or at least, had strong reservations about?

This is .. low-integrity behaviour, though? It used to be part of the operation of both ministerial and cabinet collective responsibility that ministers had a responsibility to agree or resign. The gold standard of this was Claire Short, who resigned rather than support the Iraq war: https://www.telegraph.co.uk/news/1429856/Clare-Short-quits-C...

Arguably the erosion of this has led us to the crisis of the present day.