Zombiefied Piglin spawn sometimes when Strider spawn egg is used underwater

I think it's indeed, since they rarely spawns with a Zombified Piglin riding them, just like Skeletons spawning with Spiders.

Do you mean that a zombiefied piglin is riding an top of the strider? This should be intended and does not just work in water. 

Yeah, I was testing this and it probably happens because zombie piglin spawns on the Strider.

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