Where is 'Tab for Pie Menu' Preference setting in 2.9?

This did not bother me until I had to redo my preference because of a bug. Compared to 2.83, 2.9 doesn’t look like it has the setting anymore like below.

This is really bothersome since it’s a super convenient keymap.

Normally, it is still there.

user_prefs_29

I just realized that the reason it won’t appear is that I imported a custom keymap. It doesn’t make sense that the settings is hard coded to only appear when Blender keymapping is selected and not others. I guess I’ll have to keep manually checking every update if there are any new useful keymap preference settings and then rebind my keys again!? This is really frustrating.

Options of this panel are aliases, modifying several shortcuts of similar operators as once.
Entry of keymap is shortcut, not the operator.
So, problem is that those options should be modified to work with old 2.7x keymap or Industry Standard keymap.
And the way, it works, now. Blender can’t figure out if this could work with a custom keymap.

During 2.8x development, focus and user feedback was about what shortcuts should be handled by default keymap and what option to create.
They will probably end-up to refactor way to create keymap.
But there are more important lacks (like texture baking, brush management), that are frustrating, too.
Developers are calling that the technical debt.
They try to annihilate it before Blender 3.0. But you should not consider Blender 2.9x series a lot less experimental than 2.8x series.