HD
and if a GA instruction is issued it would be folly to ignore it.
Understood, but if your "instructions" are so vital, they need to be made in good time / at a suitable point to be comprehended and actioned.
After landing the pilot was told to take a particular turn onto a taxiway
In today's world this is often too late... I have been asked by LHR ATC, on short finals, to make an early turn off. Trouble is, I briefed 45mins ago and setup for a reduced flap landing (iaw my company policy to save ~7kgs of fuel) = a longer landing roll, and if I now alter Flap <1000agl, I have to Go Around (Company dictat).
We are encouraged more and more the brief taxi routes, / vacating points etc., and it is not in our "training" to just accept a change on the rollout. Yes - some can and will try to cope, but I have seen more than one inappropriate screeching turn to comply, and often if ATC start issuing instructions on the rollout I tell my colleague to disregard them until there is a suitable space in our SOPs actions / callouts.