Key All Modified hotkey (shift-k) does not set key on Quaternion interpolations (both quaternion modes), but works fine on Euler Angles. Key All Animated works fine with all rotation interpolation modes.

repo:
-create a clip with two keys animating rotations.
-go in-between the two keys and modify the rotation...
-Key All Modified (shift-k)... rotation is keyed.
-in the AW, RMB-click the rotation property and set the Interpolation mode to "Quaternion" or "Euler Angles (Quaternion)"
-go in-between the two keys and modify the rotation...
-Key All Modified (shift-k)...
bug: Inspector visual feedback updates, but no key is created.
expected: Key is created, exactly like when using Euler Angles.