Multi-Entity Riders (Zombie Horse Rider, Zombie Nautilus Rider) Cannot Pass Through Any Portals in Bedrock Edition

Description:
In Bedrock Edition, recently added multi-entity mobs such as Zombie Horse Riders and Zombie Nautilus Riders cannot be transported through any type of portal (Nether portals, End portals, or End Gateways). This behavior differs from Java Edition, where all composite rider entities can successfully pass through portals.

How to Reproduce:

1. Use the /ride command or locate naturally spawned multi-entity riders (e.g., Zombie Horse Rider, Zombie Nautilus Rider)

2. Push the composite entity into an active Nether portal, End portal, or End Gateway

3. Observe whether the entity is transported to the corresponding dimension

Observed Result:

• All multi-entity rider compositions remain in the original dimension and fail to teleport

• No portal type (Nether, End, or End Gateway) successfully transports these entities

• Single entities continue to work normally with all portals

• This affects all rider combinations, not just the newly added ones

Expected Result:

• Multi-entity riders should pass through all portal types successfully, consistent with Java Edition behavior

• Portal transportation should work for Zombie Horse Riders, Zombie Nautilus Riders, and all other rider combinations

• The entire composite entity (both mount and rider) should teleport together as a single unit

Additional Notes:
This appears to be a systematic issue affecting all multi-entity compositions in Bedrock Edition. The inconsistency with Java Edition impacts gameplay mechanics and mob transportation across dimensions. Urgent unification of portal behavior between editions is requested.