Grist the hunger tide and containment priest

I think this is probably ( blood moon bug/dress down ) category, but when casting green sun's zenith for X=3 grabbing grist the hunger tide with a containment priest in play, grist is exiled when the static ability should only apply in other zones than the battlefield. This means grist is a plainswalker before priest sees it, so it shouldn't be exiled.

I think this is blood moon bug problem, but just another thing to add to the list of competitve play breaking bugs

Start with the implementations of Grist the Hunger Tide, Green Sun's Zenith, and Containment Priest, then trace how the engine handles battlefield zones and static abilities. Reproduce the X=3 interaction and verify that Grist is not exiled when it is treated as a planeswalker on the battlefield.

Written by the indexing model from the issue text.