Right, but some sleep move accuracies are really low. Sing is 50%, leaving it a last resort/risky sort of move. (Clefary, Lapras, Altaria, Bliss, and Jynx learn it). It's a normal move, meaning ghost types can resist it. PWO is wonky that way.
Yawn is 20% acc. so it's is basically useless unless a person gets fairly lucky. (It's on Quag, Snorlax, Slowbro, Togetic, slowking, Magcargo, Dunsparce, Kingdra, Slaking, Swalot, Camerupt, Chimeco, and Reli. You only see like 3 of those in combat often, and the 3rd is generally banned from PvP.) It's also normal and ghosts would also help here.
The pokemon that have sleep powder (75% acc) are mostly NU or UU in this game aside from a select few. (Venu, Butter, Vileplume, Venomoth, Victre, Eggs, Jumpluff, Sunflora, etc). Most of these you just never see in the metagame, and for the rest if you can't outspeed them on the next switch god save your soul. If these things kill your pokemon, they're probably switching into you and you can return the favor upon next switch. If you can't, it's near the end of the game and you have an iffy matchup anyway.
Hypnosis' accuracy is 60%. The only pokes really considered any viable threat in PvP that learn it are like...maybe Gengar, Eggs, and Garde (?). Either way, hypnosis shouldn't work on dark types, because it is a psychic type move and PWO is weird like that. Gengar and Garde aren't exactly tanks either, so a single miss could end them. And eggs is, from what I have seen, fairly simple to counter/outspeed.
So I think there are definitely ways to wall these pokes unless you just get a bad/unlucky start. The worse move is sleep powder, which you cannot type-resist. But, it also has a 1/4 chance to miss and is generally on slower pokes. Pokes like Venu/Eggs would use these if they had a bad matchup and pray they got lucky.
And then you're left with the argument that sleep powder, NOT sleep, could be overpowered if somebody got on a luck streak. You then have to explain how often these streaks happen, how they cannot be countered, and how we could balance that one move...if it's even worth the hassle to nerf it currently and then unnerf it when more updates come in.
EDIT: Forgot to research spore. Give me a minute.
EDIT2:
Spore is 100% accuracy, which is terrible an does lend one to think it is OP. Then again, only Parasect and Breloom learn it, of which only Breloom is potentially used in PvP and has the power to actually kill teams. Sooo...