Doflamingo comments on Sanjis strength and attacks whilst he did not use CoA when blocking.
Doflamingo in his thought process as Luffy was about to Jet Gattling him, remembered Sanji amd used CoA because Luffy is the stringest of all of them. The CoA was not needed tbh, Doflamingo didnt even say his attack was ok. He still views Luffy as crap.
Jet Gattling isnt a basic move but Doflamingo was still smiling. Last time when he had his coat like that he pulled his otherbhand out using parasite+Overheat.
As someone said, this is the alliance saga do dont be dissapointed if it is a tag team. "It will make Luffy look weak", regardless of if he defeats him alone or not. Luffy is too too far from facing a Yonkou tag team let alone solo.
–- Update From New Post Merge ---
@RamistaR:
It looks like a string indeed, but maybe it's because I want to see one
As for Kaku, he used Rankyaku with his leg and swords with his arms. Because he can't use Rankyaku with his arms.
If Doffy can use strings with both arms and legs, he has no need to learn an advanced martial technique that does the same thing.
I spent a good ten minutes staring at that and even had non one piece readers and viewers opinions on if that would be a string or such, they said yes.
It didnt look like he had a string against kyros but it probably was.