Polymer + ViaFabric 1.20.4 seems to not omit experimental mobs for Fabric 1.20.2 clients

[Ampflower]

See: Modflower/Polysit#7 as initially reported by @ArkoSammy12

Steps to Reproduce:

• On server:
  • Use Minecraft 1.20.4
  • Install Fabric API, ViaFabric, ViaRewind, Polymer, any Polymer-based mod (i.e. Polysit, Polyfactory)
    • It seems that any registry modification is required, as bare Polymer doesn't trip the bug.
• On client:
  • Use Minecraft 1.20.2
  • Install Fabric API; the vanilla client seems unaffected
• Start the server with the given mod set
• Join the server

Expected results:

As a vanilla client would do; join perfectly fine

Actual results:

Claims a conflict on the Minecraft namespace regarding the Breeze and Wind Charge.

Other things of note:

The registries it conflicts on seems to always be the registry modified by mods

• Polysit only trips the entity registry
• Polyfactory trips the block registry

It seems that 1.20.1 clients get mangled entity data handlers

Logs:

From server - not particularly helpful for more than versions

From client

ViaVersion dump

[Patbox]

I imagine it doesn't fully cancel full logic, but to be fair it also is kinda issue on ViaVersion part for not canceling that packet entirely

[Ampflower]

Fair; was just about to duplicate this issue there in case it was more their end rather than yours.

[Kichura]

marked the external issue as "help wanted" cuz the via dev team refused to do anything with it, as for myself - i do encourage requesting for help on how to solve it.

[Kichura]

Fixed.