>>36771542Actually it doesn't allow one more Dialga.
Arceus creates the trio again, but for that it has to create another universe, so their power can work in this new universe, without having any influence in the ours. Remember that even if Dialga or Palkia or even Giratina are from another universe, they still can live in an universe different from their original one. That's why we can catch one of them without any problem.
