You dont know that sanjis lineage factor is recent plot, oda has had sanji backstory ready way back when the SH entered the grand line and theres a high chance that oda always had sanji being expermented , also theres higher chance that everything with amabakaa was thought up close to the time skip and the concept of sanji being modified has been around since he was creation and the germa and that lineage factor is explaining how sanji is able to use DJ something his had since enies lobby, yeah because him able to fly didnt help anyone
and him being stronger than he was pre ts didnt help anyone.