I am happy to hear there is going to be several ways to escape. But if going back and forth is going to be 'trivial' then why make it a point to showcase the restriction in the very beginning, when they had given literally 0 other information out. It is mildly rhetorical, because I think I already know the answer: the same reason Trump says -anything-. Even negative attention is better than no attention. Personally, I've spoken to a handful of people about season 4, and pretty much the conversation has been the same every time...ravenloft...gothic horror...bad ass vampire dude...probably lots of undead...some really stupid(so far not completely explained) rule about characters being trapped in the plane. Well, why would they...oh, right. Dawnbringer. Maybe the other 80% of the conversation is considered a net positive.
BTW, all the cards appearing on the book cover and in some of the other iconography, and the suggestive titles of the modules reminds me of a whole campaign idea I remember from a long time ago. Somehow, a Deck of Many Things has become split into individual cards, and the villain has figured out a ritual to reunite the entire deck and activate its magic. The ritual will allow him to PICK which cards he draws. Ever since I've been a gamer, Decks of many things have always been treated akin to Divine magic...aka God-level Wishes etc. So in this case, what if BBEG wants to escape Barovia...or better yet, he wants to merge his plane with another, thus corrupting it with his evil, undeady, magicky ravenloft stuff. The only problem is the cards are scattered across the land, attracted to strong magical forces, guarded by powerful creatures. Enter the PCs...