First of all we already saw normal person fighting against a giant, multiple times, gunko vs loki, imu vs broggy and so on.
Second the sh will (like zoro vs nusjuro who is a big fat horse is practically confirmed) and have fought against the gorosei, whose zoan form are this big, BIGGER than dorry and broggy
this "oda will not do this" is already disproven in the manga
@MonochromeYoru