In the End, when an armor stand with Frost Walker enchanted boots is pushed across the 2048 chunk boundary, in any of the cardinal directions, away from 0, 0 the enchant effect reliably stops being applied to nearby water. It is not clear if this occurs in other places, but it seems consistent in all four directions at this particular chunk/region boundary. This behavior appears to continue where the effect will no longer apply to nearby water when pushed.

This was tested both on a local server running carpet mod as well as in a completely vanilla single player world. Attached screenshots are from the former.