Ash has been gushing over a lot of mon, while he didn't actually got them.I remember when Ash was absolutely gushing over Yamper when he first saw it. Not surprising that he'd want one.
Still don't see why he needs one tho
I don't think that poster actually means something (Also: Yaayy Galarfetch'd is finally on a poster, but poor Gengar), unless Ash and Goh are gonna move from Kanto to Galar and are gonna live with Prof Magnolia, but in that case they, would have shown Mimey on the poster as well.