WMG / Summit Apocalypse

S-Flamingo isn't made from Doflamingo's DNA

S-Flamingo is shown to be clumsy, a trait we don't see with Doflamingo. Doffy is a Warlord who was confirmed to be involved in all sots of unsavory business like slavery. It's not implausible he was also involved in drugs and may have also been a user. This could have lead to the blood samples taken from him being deemed too contaminated to be of use so they used Rosinante as a donor instead.