That's if you equate a rebound or a block as equal to an assist. Numbers are an advantage for Ionescu IMO when you factor in the value of her assists as well as her overall impact on the offensive end. Numbers wise it's:
Ionescu: 19.3 ppg, 8.0 assists, 7.2 rebounds, 1.5 steals, 2.5 turnovers, 0.2 blocks, 45.5% FG, 44.7% 3pt, 87.5% FT
Collier: 19.8 ppg, 10.2 rpg, 3.8 assists, 1.5 blocks, 1.4 steals, 1.8 turnovers, 61.2% FG, 22.7% 3pt, 68% FT.
Then you have to look at players like Durr, Ogunbowale, and McCowan, all of whom have POY worthy numbers as well and are on top teams. It's far from a 2 man race at this point, there are a lot of great players having fantastic seasons right now.
Most on here want Collier to win, which is understandable, but my guess is that across women's basketball most believe Ionescu is the deserving winner if the season ended today. She has been magnificent in big games, her all around stats are off the charts, and she's the best in the nation with the ball in her hands.
Side note--I think UCONN matches up very favorably with Oregon State. UCONN's weakness is size inside, and Oregon State relies heavily on perimeter scoring and 3pt shooters. A more dangerous team is one that is going to dominate the glass and has a big offensive presence inside.