Yes, it truly is.
Is he unwilling or rather not satisfied with the physical and speech therapy?
Sometimes the willingness to seriously engage and participate longterm and the progress made also depends on the therapists one has to work with. At least that is what I witnessed with my DH.
After the second serious stroke he refused to go to stroke rehab again (after the first he spend there almost 8 weeks in addition to the weeks at the hospital) so we did the exercises and speech therapy at home and invented a few of our own to add some variety and entertainment.
Of course, the bouts of anger and frustration arise every so often as many men define themselves and their self worth through their physical strength, manual skills and abilities.
But declining strength and skills also come with age and we all will have to accept and adapt to it some way or other