I can’t speak to the technicalities (since I’m not a backend engineer), but Darktide was made with Xbox to PC in mind with crossplay (at least in terms of Gamepass iirc), Vermintide wasn’t. So each has it’s own “backend bucket” for lack of a better term, so accounts are separate. It’s a bit hard for me to describe without the correct vocabulary and specifically going into detail how accounts are set up, but yeah (speaking as someone who has had to perform some tasks in there now and again while employed there).
Is it possible? Sure. Anything is possible within the world in programming, but the amount of effort to do that is very very high, unfortunately. Accounts aren’t linked in the same way Darktide is (which has a different backend platform). The networking setups between the three platforms are also very different for V2, and at least in terms of crossplay, their balance is different as well.
I think it’s also important to note that V2 is quite old now, so even if they did manage to make this happen, the payoff from the business sense probably isn’t worth it. So really not as
“pathetic” as you might think. V2 would likely need to maintain a very high population between all three platforms (think Destiny or Warframe level of players) in order for this to make financial sense, since it wasn’t built crossplay first out of the gate.
If you think about it, the Tide franchise, like most games, iterates upon itself; not just in gameplay but in tech as well. V1 > V2 (different backend but no crossplay) > Darktide (which has crossplay).