For most of my family and friends it would be on the tail end of that window. A lot of them have small children so timing often runs away with them a bit. Anything up to 9.45 wouldn't bother me, later even as long as they'd messaged. I'd hate people arriving before the start of the window - I'm autistic and it always throws me off if people are early.
People travelling further are more susceptible to traffic so might be a bit after it, but they'd generally all message and let us know.