>>43748578Considering Slowbro was the second Pokemon ever created iirc, makes sense. Also, Slowpoke line had been shilled since Gen 2 at the earliest, with the Slowpoke Well and Slowking.
>>43753979Game Freak likes to switch up primary and second typings lately. You have stuff like Galarian Mr. Mime and Mr. Rime that by, all in all accounts, should be Psychic/Ice since they were originally Psychic-type mimes that gained Ice-type characteristics. You also have Obstagoon and Alolan Raticate, which are Dark/Normal instead of Normal/Dark, despite the other members of their species around the world being Normal. (And in the case of Alolan Raticate, its species were brought to Alola from elsewhere, so unlike Obstagoon, the regional form of Raticate is the newer one.)
Oh yeah, Game Freak likes switching up Flying type now; we now have three fully evolved dual-type Pokemon lines where Flying is the primary type.
I suppose the logic of this Pokemon being Poison/Psychic in universe is that Slowbro's Psychic-type characteristics are really just a personality trait for it. Slowpoke, Slowbro, and Slowking are Psychic-type hippo/hermit crab monsters that only manipulate Psychic energy due to their brainwaves being off. They can't consciously control their Psychic-type power. Conversely, Galarian Slowbro can consciously manipulate the poison in its body and fire it out of the Shellder gun on its arm. Slowpoke, Slowbro, and Slowking are also Water/Psychic even though these Pokemon were originally terrestrial Pokemon that decided to live by the coast in order to fish and eat. So you have Slowbro and Slowking also having Psychic as their secondary typing, much like Galaian Slowbro and probably Galarian Slowking as well.