According to Colin Moriarty such a system is "asinine".
It kind of is, if you actually prioritize software sales. It basically cuts out a lot of revenue and doesn't account for costs in associated labor for porting between different platforms or adding features to take advantage of the platforms being ported to.
Once again, people cannot take the way Microsoft do certain things in the gaming space as the "fully sensible" way to do them from a business POV because gaming revenue accounts for peanuts of MS's total company revenue. They can essentially afford to tank any such losses in distributing PC-specific and console-specific software SKUs. Companies like Sony and Nintendo, where gaming actually accounts for a much bigger part of their revenue (or virtually all of it, in Nintendo's case) can't necessarily justify that type of model considering other company sectors don't generate enough revenue to offset potential losses.
I do think Sony will provide a discount for those who buy both PS & PC versions though, so maybe instead of full-priced on both you get a 10% discount on both in some bundle. Somewhat similar to the discount Microsoft provides for purchased games that are currently in the GamePass rotation.
Shared licenses and saves are coming! Buy on PS5, play on PC, save on PS5, continue on PC.
Sure, if you buy the game on PS5 and also the PC version. Cross-buy as a business model just doesn't make much sense when you think about it, unless you're a company that already gains very little from those sales in the first place.
Anywhere else you look, Cross-buy isn't a thing. Sony used to do it with PS3 and there was little traction. Nintendo doesn't do it (otherwise they'd of allowed Switch owners who bought Mario Kart, Smash etc. on Wii U to get the Switch version for free), Rockstar doesn't do it (GTA5; 'nuff said), even Bethesda don't do it (all those Skyrim re-releases; you really think many of those aren't from people who already bought it on PS3, 360, PS4 etc.?).
Not sure why people expect Sony to buck that trend just because Microsoft has. Microsoft's 1P software simply wasn't selling at high volumes in the first place, game software revenue has historically been a pittance for their bottom line so losing some quarters out a bag of quarters means little when you're mainly trading Benjamins. That's the real reason they allow Cross-buy.