I don't think Marriott has to offer guaranteed checkout. SPG is the only one to offer it.

For Hyatt, it is a 2 pm checkout for all GP members (versus the normal noon checkout), subject to availability. I have had a hard time getting this on occasion as a diamond member when a property was quite full. Marriott does not specify a checkout time, but I have had few problems getting an extra 2 hours.

I have read on FT that getting a late checkout from Hilton can be quite hard at some properties. I do not recall Hilton offering any guarantee or even a promise of late checkout for elite members. In my limited experience at Hilton properties, I have found it hard to get more than an a hour extension for checkout.