Recall that the M1 had such a huge impact on the Macs re: battery life, because it was compared to Intel chipped laptops.
The iPads have had A-series chips for awhile, so shouldn't expect any type of similar leap in battery life going from A12 > M1. And it seems to be the case, as officially the new 11" and 12.9" iPPs are still 10hrs with their standard "surfing web on Wifi or watching video"