He gives Luffy powerups then nerfs its powers multiple times. Thats not masturbating. Oda gives G4 that overpowers Dofla only to give heavy side effects and stupidity. Oda gives Luffy the weakened G3 - nerfed by seawater- and it reached the size of Kraken in Fishman Island, but the supposedly not-weakened G3 suddenly shrunk to boulder-sized when he fought Katakuri. Oda gave FS to match YC1s but suddenly other chars like Zoro and Sanji can catch up and fight YCs comfortably for no reason, struggle, or proccess after all those chapters of Luffy fighting extremely difficult against YC1 for 20 chapters.
If Oda was masturbating to Luffy, he would have pre-timeskip Luffy having speed faster than lightning since Enel said "its too fast!" to his Gomu2 Golden Rifle while unable to dodge Luffy's attack even when Enel has lightning speed. But apparently not. Since if that is the case, Oda would make Luffy matched and even beaten Kuma and Mihawk since pretimeskip just like how Luffy beaten Croc-Moria since both are Shichibukai.
If Oda masturbates to Luffy he would make Luffy buldozes-oneshots through Dofla-Cracker, beat Kata from the start of G4, and make his only struggle against BM and Kaidou and even then Oda will make Luffy won against BM since the first time in WCI.
Oda also won't have Luffy unconscious for so many times after being oneshot by Kaidou even in G4, instead Oda will have Luffy snicker when meeting WSC since Luffy finally meets a challenge, just like how Zoro snickers around when fighting without meeting any real struggle or consequences or meeting a superior opponent who is actually pay attention to him or focused on him.
If you said Oda masturbates to Luffy, do you also think so when Kaidou oneshotted Luffy with Thunder Bagua or when Luffy fell unconscious from Onigashima? Don't you say that Luffy is trash instead? Did you say Oda masturbates to Zoro when Zoro try to block Hakai for 1 sec, then scarred Kaidou and said that it was shitty writing? Because Zoro doing those two things are, regarding the writing, Zoro's narrative counterpart of the current narrative Luffy matching and finally surpassing Kaidou, something that Luffy must do in order to be PK.