390k PS5s at an average selling price of $480 translates to 681k Switch units at an average selling price of $275. An ASP of $265 for Switch would result in 706k units sold. If the PS5 did notably better than 390k in March, then Switch sold more than 700k in any case.
I don't remember how big the year over year lead was that Switch built during January and February, but 2021 is faring well either way.
Best numbers we got
Jan: 385k + Feb: 614k — 999k (2021)
Jan: 270k + Feb 338k — 608k (2020)
for H1 2020
Jun: 365k (major shortages)
2020 H1: 3311k
If NSW was at 700k in March, it needs another 1612k to match last year or 537k avg monthly