If you think Apple wants to do something nefarious to users of their hardware, don’t buy or use it.

If they can’t be trusted, they don’t need to add opcodes.

Well the point of the question is trying to establish if it’s even possible in the first place. If there is no credible way, then there is no need to fear there are nefarious reasons for implementing such a change for either Apple or Microsoft, outside of restricting third parties. If there is, then it’s as you say.