In my opinion people always make this way too complicated. It’s not impossible to guess “ballpark” numbers.
The consoles are tied. We know this because both consoles sellout instantly.
If PS5 sold about 20 million then so did Xbox with perhaps 3 variables.
-variable 1 Xbox waited longer to begin manufacturing (rdna 2 / red ring style precautions)
-variable 2 Xbox created a next generation cloud with Series chips (I would personally argue that these chips should count in the sales totals because that would simplify things when trying to compare the PS5 and Series numbers. PS5 will never have a cloud because PlayStation will never be willing to sacrifice these guaranteed sales like Xbox was willing to do, so why not just include cloud servers in the sales totals?).
Variable 3 - Series S is beginning to become more available. (Some would argue that this is a knock on the Xbox Series S but I think these consoles are also guaranteed sales but they will just require a big AAA release to move consoles. Every time there is a new Elden Ring then the shelves will empty. It’s a more cyclical strategy but just as effective in the end as it pertains to considering number of consoles sold).