If management is looking for reasons to dismiss him, I.e take him down the disciplinary route for under-performance, hinting that he's "under par", given his service duration of 3 years, they will have to formalise it according to their company policy and process which is:
- First informal verbal warning with specifics on aspects for improvement, then after a period of time, if improvements have not been made,
- First written warning, formalised with a PIP (Performance Improvement Plan).
-Final written warning before actual dismissal.
If they haven't even started this process then it puts them at risk if they take action along disciplinary lines.
If they go for redundancy, then he needs their confirmation of the details, including the fact his role is being eliminated etc. If it's all so vague, until they actually declare their intentions, all he can do is watch and wait.
As regards the hospital appointment, it's impossible to say how that might influence their decision making. It shouldn't under normal circumstances but it sounds like they aren't being transparent or communicative, so there's little to be gained by speculating. If he needs the procedure, his health comes first always, and he should seek approval for absence in the normal way. It won't make it any "easier" for them to dismiss him, if all it includes is 1 week in hospital and 4 weeks working from home.
It would be worth his GP giving a Fitnote to validate the recommendation for him not to drive. If they really get difficult and insist on him being at work (and he is up to sitting in the office) could he get a taxi 1 day per week to show willing?