Original summary
Frost Walker On Armor Stands Only Partly Functional

When an armor stand is equipped with frost walker boots, it should be able to freeze water (just like a player would), how ever this is not typically the case.

When pushing the armor stand next to water, nothing will freeze.

When dropping an armor stand from above, nothing will freeze.

The only way that has been found, is to launch the armor stand on slime blocks, but even this has very buggy behavior as it freezes water several blocks below it.

You can find a detailed example of this bug here: https://youtu.be/-w1Kf--Alv4?t=494

Regardless of the bugs with frost walker, I would also like to mention that this is not on parity with the java edition in nearly any way <3