You are pretending to be dumb to troll? or you genuinely didnt even bother to read what i said?
I will repeat myself just in case...Oda keeps adding new forms of G4 at every damn fight Luffy gets, we saw one vs Cracker, we saw even another one vs Katakuri and we might even see goddamn G5 in this arc.
This is a classical case of asspull powerup, adding a new form everytime the character struggles, dosent matter if Oda tries to justify it with "he had it since the timeskip" in the end of the day its just oda's justifying a new powerup he pulled out of his ass, like dragon ball and its goddamn super sayian forms, every damn villain requires a new transformation to beat, and its the same with Luffy. Sanji's diable janble and Zoro's Asura might also make no sense just as much as Luffy gear's but at least they dont show new variant of it every damn time they fight someone.
While i do agree most powerups in One Piece are asspulls one way or the other, the two allternate forms we've seen of Gear 4th could just be improvised on the spot by Luffy and it would make sense on the story.
Boundman is the base form he's had since the timeskip and the one that could've been either an asspull or something Oda planned but waited for a certain moment to reveal, which retroactively affects the previous arcs where he didn't use it.
Tankman came about from how much he ate during the cracker fight, it's just boundman but super fat, even the humor during that scene makes it seem like he just improvised it.
Snakeman was something he probably came up with during the fight with Katakuri to counter his FS, which doesn't have to be an asspull because they fought for hours beforehand and got experience with it.
If he pulls out another form against Kaido, then similarly it would just be a sidegrade to regular boundman made to counter Kaido's toughness and utilize Ryou better or something, but it wouldn't be something he's had since the timeskip.
Boundman is most likely the only form he developed during the timeskip.