How does Medicare judge progress in therapy in a rehab center?

My 91 yr old father who is in a rehab facility is receiving therapy in swallowing, OT and PT. I think the only one they are pleased about is swallowing where he is moving from pureed to textured foods. But in OT and PT he sometimes has a "bad attitude" because he doesn't get the bigger picture and refuses to participate or doesn't get it. He is not where near being able to walk. But swallowing is obviously pretty important too For Medicare to continue approving his 100 days would clear progress in swallowing justify a continued stay?