Starting March 30th 2020 Microsoft has introduced new technical and policy changes to (custom) skins in Minecraft multiplayer. This affects players that use skins with custom geometry, sometimes called "4D Skins" in the community.
Marketplace Skins, Hive Costumes, regular Alex/Steve retextures and Persona (Character Creator) skins are NOT affected by these changes. We continue to apply Hive-side filters to all skins - this may block some extra small or big skins that are allowed on different servers.
Players that attempt to use custom geometry will be shown as regular Alex or Steve skins to other players.
This does not affect capes.
This is Microsoft policy and not up for debate with Hive staff.