There is no denying that obviously EG needs to comply with Sony's policy.
The reality is that EG did indeed comply because they wanted the userbase and of course the massive financial gain that came with it. So EG are not without fault, and anyone trying to cushion them from the backlash is either oblivious to the obvious or are set on making Sony the sole target.
Sony set a policy, and EG agreed to it. They are both a fault in one way or another.
And yeah, at least the NDA suggestion is a lot more of an answer than 'maybe EG just didnt know what they were getting themselves into because they are a small little company who dont know any better'
This still does not eliminate the possibility that the agreement between EG and Sony on how Fortnite would be handled on PS4 had been concluded long before a Switch port even started consideration... By the time Switch port started work, dealings with Sony may have already concluded. Too late then, Switch access to a PS4-associated EG account was not discussed at the first round of dealings.
I sincerely think EG wants cross-platform and cross-access so that their players can move freely across platforms. It only makes sense to have this to maximize playtime and therefore, transactions. To lock players down to a platform and place limits, on the other hand, benefits a platform since players are now forced to use that platform.
EG has some blame sure but it doesn't make sense to me that they would ever want this situation to occur. I cannot say the same for Sony that has the greatest clout out of the big three.