Is this a question or as conundrum?
Ambulate means to walk or move around. Sat up out of bed isn't ambulating but it does get the circulation moving and lessens the risk of thrombosis.
It doesn't really matter much in our local hospital. They have you up, moving around and back home ASAP so they can use the bed again for another patient.
If you then die at home it doesn't affect hospital statistics and is 'someone else's problem'.