What has happened to me in those cases is that Architects lumped on a lot of extra nice to have things which would certainly have made us fail the time constraints. It was completely un-agile and I only got things done on time by demonstrating very clearly that time sensitive work is not the place for grand refactoring and at last winning over the main architect.

When there's a time constraint one has to be able to winnow out the real must-haves from everything else.