You're making the Claim, not me, so if you want to prove something, you share the Panel.
What We know for a Fact is that Sanji Unlocked Exoskeleton in Onigashima, you're the one who assumed that it got Disabled after his Fight, something that his Siblings never shown doing, nor was it ever stated, if you have a Panel showing Sanji lacking Exoskeleton after Onigashima, i'd be happy to change my mind
Oda can make Illustration Errors but it's not my job to assume a Panel that i don't agree with is an Error, unless it's an obvious mistake.
For example, there are People who said Venus White Sword is an Error, i have no reason to assume it was, same case here.
So there is difference between "I couldn't answer your question" and "Your question isn't valid".
If you want to say that "Exoskeleton" is Temporary Power-Up or requires Activation, then show me a Panel or Statement where any of Germa Children demonstrate that.