Something that just crossed my mind:
Momonosuke's fruit, while a ryu, is unlikely to be exactly the same as Kaido's since the latter is revealed as the Seiryu fruit, the blue dragon. Momonosuke isn't blue, and it's not like this is a minor detail because such color is very important in distinguishing Seiryu from other ryu.
So either Oda will ignore this detail, or Momonosuke's fruit doesn't directly mimics Kaido's, or Vegapunk just worked with the "ryu" DNA, whatever that is, but couldn't/didn't want to produce a Seiryu artificial fruit.
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Or Oda is just messing around with a half trolling, half serious answer. This is the same guy who said he named Rocinante on a whim even though it's obviously a way more well-thought name since it perfectly fits the whole character. I'm not saying he's literally spoiling Gear 5 is about to be revealed, but his trollings aren't that simple.