Reproduction:
1) Open any HDRP project
2) Attach Light Anchor component to one of your lights
3) Edit distance field
4) Undo

Result: light moves, the float values does not change
Expected: light moves and the float value is also reverted

Bonus: In the video, notice at the start distance value is 3, at the end of the video I input the same value of 3. However, the light position does not match what was at the beginning of the vid.

Unity 2021.2.0a18 with prepackaged HDRP