Of course it's not smooth, which is why they've been working on the turnover since midway through last year. The info in the steam post isn't some form of "Oh btdubs, we're dropping the current stuff for UE5." It's "The UE5 version, which you guys have been aware of for nearly a year now, is finally approaching a stage where we can share it."
not sure why they are so obsessed with ue5, engine changes are never smooth no matter what epic says
wild life engine transition also had major issues
UE5.1(NOT UE5) is really convenient for what they want. UE5 at first was really bad but as stated in their blog they didn't jump on it right away because of that. They clearly have some restraint. Besides, they put up polls to see what people wanted, it's not like they're dropping everything and switching over. Overwhelmingly people were fine with the upgrade as opposed to updating both at the same time or staying in UE4. They're pacing out their updates and leaving the UE4 branch available as the UE5 version will be a lot more structured and less of a demo. They'll start you off with an introduction quest, each faction will have their questlines, and you'll be able to unlock what UE4 already has by default due to its state as a demo, etc.
I don't understand the penchant for comparing things out of pocket like that.
Last Devil swapped out from RPGM to Unity and it's fucking insanely good due to how bad RPGM got with performance and all the up to date functionality Unity provides and that's between two totally different things that aren't even related. Comparative arguments don't work most of the time because a more outlandish successful one will pop up to counter it, it's bad logic. That's not to say I'm blindly following this. I have it wishlisted on Steam because I like the concept and until it's something worth playing I'm not dropping a dollar for it. I use this site as a demo download service more than anything else but so far I've seen consistent updates and improvements unlike in Wild Life.
P.S. Let this be clear though, this is far beyond what Wild Life thinks it is, it's already a game with some semblance of a plot and quests, as well as context-based scenes and a functioning, albeit slightly janky world. This is not a set of models with sex animations on an open, oversize sandbox map with nothing to do in it but use hotkeys to make your own fun. Wild Life switching over to UE5 immediately as opposed to waiting for its initial growing pains to be ironed out was their mistake as it would buy them time from all the "debugging" they'd have to do. The blog post/changelog linked in the OP even mentions that explicitly they don't want a month of debugging as the initial impression to the game.
Ramble ramble.
tl;dr these people seem to have some restraint and planning while Wild Life's been an uncoordinated mess from the start.
They're incomparable, but I'm also not getting my hopes too high up, cos I'm not blind to how these projects die as well.
Man that was a lot more typing than I meant to do.