Using a standard Samsung 25W charger with S20 Ultra I got 10-100% in about an hour. The two phones should perform comparably at 25W but that isn't the case.
My test with S21 Ultra:
10:51pm - 29% battery
11:29pm - 39% battery
I feel like 38 minutes to charge 10% is unacceptable. The entire time the phone shows an estimate of 48 minutes to full charge. Oddly enough using the Samsung wireless charger the phone does charge in about 50- 65 minutes.