Or so says Todd Howard, in the vaguest way possible, and un-reinforced by his own PR department as yet
https://www.cnet.com/news/fallout-76-wont-have-cross-platform-multiplayer-because-of-sony-says-director/
I'd put it as more likely their frakensteined mess of two engines can't handle it and its an easy out, myself. Not because Sony's stance is unlikely, but Sony's stance has never included blocking PC crossplay, and shouldn't impair Xbox/PC either.
https://www.cnet.com/news/fallout-76-wont-have-cross-platform-multiplayer-because-of-sony-says-director/
I'd put it as more likely their frakensteined mess of two engines can't handle it and its an easy out, myself. Not because Sony's stance is unlikely, but Sony's stance has never included blocking PC crossplay, and shouldn't impair Xbox/PC either.