2 things: If Nintendo has a store on PC - you could buy all those 20 games on there. They'd still get the same cut. I know you said physical games, but is that really the future? For me - I actively avoid buying third party games on Nintendo at this point, and I haven't bought physical games in a couple of years now on Switch. Early on, yes, I bought some third party games on Switch (and regretted it sometimes, because of performance problems, which yes, contributed to buying less on Nintendo hardware.) I basically don't buy anything other than first party Nintendo software on Nintendo any more, because I know it'll go away in the next generation, like with my Wii U library, unlike the things I buy on Steam, Epic, or whatever else on PC.
The other thing - yes, Nintendo makes some margin on their hardware (rumors are that they won't make as much on Switch 2) - but how much? I don't think that applies to Sony - I, and I imagine many others, don't even want Sony's hardware any more. It's a closed platform, and I don't watch DVDs or blu-rays anymore - which is the only reason I even got a PS3 or PS4 - even arguably the PS2. (Don't get me wrong, I loved to game on the PS2, but it's been a downward trend on PS3 and PS4 - while I still game plenty on PC, and yes, plenty on Switch.) I will not buy a PS5, as frustrating as it is to wait for some of those exclusives to trickle down to PC. If they never arrive on PC, so be it. I got a deep backlog.
I maintain, it makes ZERO sense for Sony to release their games on competitors' PC store fronts. It makes ZERO sense for Nintendo to spend so much suing emulation enthusiasts, rather than spend the same money on a PC storefront. Either of them have such deep first and second party libraries to leverage, they could easily muscle in.