[KRWolfblade]

I think with Zi-O II not looking like Oma Zi-O could be the fact that Sougo has yet to obtain and use all the Ridewatches of the 19 Heisei Riders. When he meets Oma Zi-O, the latter has three Ridewatches that Sougo did not come into possession yet at that time (Kuuga, Kiva, Ryuki) and it was mentioned that Geiz stole the Ghost and Drive Ridewatches from him (Sougo gets the Ghost Ridewatch in the present day in the 2nd Ghost episode).

So at this moment, he has the time manipulation powers of Oma Zi-O but not all of his power.