Portal entering is instant when riding an entity

works as intended according to slicedlime video and the simple logic that non player entities teleports instantly upon entering a portal 

slicedlime's videos are not a source of intended behavior; he simply states the current behavior of features.

He is a Mojang employee, but his videos are unofficial, and he makes them in his spare time off work.

Aside from that, it could still be WAI from the behavior of non-player entities teleporting instantly, just the note of slicedlime's videos not being a WAI source.

Seems like players riding an entity override the playersNetherPortalDefaultDelay gamerule. The solution here could be making the gamerule affect entities with player passengers, but that'll break minecart behavior. Adding another portal delay gamerule which only affects players riding entities specifically could work, but that'll be a feature request.

Can confirm

Thank you for your report!
After consideration, the issue is being closed as Working as Intended.

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