Yeah you’re right for Orochi and Onigumo I totally forgot about them. For Pekoms I don’t know he seemed to just turn back into full zoan into his shell.
But yeah you’re Right some Zoan did the partial transformation.
But frankly the biggest majority of them either went full beat or hybrid and didn’t just transform a limb a leg etc.
Marco was the only one to do that to this extent : one leg, one wing, just wings, both legs, both legs and wings,one leg one wing, full beast etc.
For me it shows good mastery.
But he never went « full » hybrid.
And King seems to do the same
Pekoms has only transformed partially as his whole lion body remains but his back is turned into the shell; we see it in Fishman Island but, if you want a more explicit depiction, the fact he protected himself from Bege's bullets means his back was a shell in this panel:
Funkfreed, too, has shown at least two hybrid transformations: one with legs, one without them.
King's case remains to be seen, though, because for him to be comparable to Marco or Onigumo (let's stick to experienced users for the sake of your argument) he'd need to actually show control over partial transformations. I mean, one thing is growing spider limbs like Onigumo and that's it despite having the ability to further transform (as he's later seen with spider abdomen), or deciding whether you want your legs to be human or phoenix like Marco, but nothing so far suggests that King is going to show a different hybrid than this.
The moment King, I don't know, grows pteranodon wings on top of his feathery ones, or a beak, or whatever, then we can talk. But nothing supports for now that this form is a "partial transformation" instead of Oda's weird twist to his hybrid, just like Jack's mammoth centaur. In fact, it isn't new for Oda to play on his classic hybrid designs, especially in recent years: Maria, albeit from a drug; Jack's centaur; Who's Who full sabertooth head...
For all we know, and as much as I'd hate it, this King form with pteranodon crest and winged arms may be his full hybrid.