A good strategy would be to showcase the new feature with the greyed out buttons in a single major version as it’s being done now and hide it as suggested for all following releases.

I respectfully disagree that that is a good strategy.

I think it makes a good user experience, because it informs you that there are situations where those buttons will be enabled, but you aren’t in one of those situations right now.

Good point, but one’d only need that information exactly once.
After that it does nothing more than unnecessarily bloat the dialog box and toy with muscle memory.
There’s better (but admittedly more tedious) ways to inform the user.
A good strategy would be to showcase the new feature with the greyed out buttons in a single major version as it’s being done now and hide it as suggested for all following releases.

I think it makes a good user experience, because it informs you that there are situations where those buttons will be enabled, but you aren’t in one of those situations right now.

annoying enough for me to downgrade

Seriously? Something like this? That seems extreme.