Some zombie related mobs can be summoned with speed if spawn event is included

Zombies, zombie villagers, and husks summoned with /summon command with a spawn event included in the command prompt will have speed when summoned. I don't why this happens, it only happens with those 3 mobs with any spawn event.

How to replicate:

Enter chat, then type “/summon [zombie, zombie_villager, husk] ~~~ ~~ [Any spawn event (including “…”)] [name optional]” and then enter. When summoned, the mob will have an abnormal amount of speed, even though speed was not put on the mob. The expected out come is that the zombie should have normal speed.