Except that it was also established that the modifications never manifested on Sanji.
They only did AFTER he used the RS. Besides, there's still a lack of explanation for the DJ. Is it due to the modifications? If it is, why did it manifest since pre-TS, but the exoskeleton never did?
He was weak up until he decided to get strong and train under Zeff to help him with the Baratie.
After that, the progression was just fine. The DJ was something out of nowhere, but Sanji was always as strong as "a strong character" could be by One Piece standards.
So...there's that.