Sony isn't known for being the most open-minded platform holder in the gaming industry. The company jealously guards its hardware and software against third-party interference whenever possible.
Indeed, the company has consistently blocked users from playing games with their friends on other consoles by taking a hard stance against cross-platform play, and it initially blocked Fallout 4 mods that used external assets.
Sony even blocked Fortnite PS4 players from using their game accounts to play on the Nintendo Switch, effectively locking them into Sony's ecosystem (and vice versa).
In an attempt to mitigate backlash, Sony recently gave its side of the Fortnite story - at IFA last week, Sony CEO Kenichiro Yoshida said the following:
On cross-platform, our way of thinking is always that PlayStation is the best place to play. Fortnite, I believe, partnered with PlayStation 4 is the best experience for users, that's our belief.
Though it's nice to see Sony speak up on the matter, their explanation is a bit strange. As Yoshida himself noted in other statements at IFA, Sony does offer cross-platform play for other games, so why is Fortnite any different?
What unique aspect of the game makes it best played on the PlayStation 4 over other platforms? Furthermore, even if you accept that the PS4 does offer the best Fortnite experience, that doesn't explain why Sony would outright block its users from playing with gamers who use other consoles.
Regardless of how unusual the situation is, it doesn't seem like Sony will be changing its mind anytime soon.