For starters I've gained permission from
@SSJRyu1 to show his
support for this CRT from our PM's, in the case anyone was doubting what I said before.
A black hole does not qualify for a pocket dimension. A black hole is just as it's name implies it to be, it's a
black hole. Mechikabura absorbing a black hole into his body doesn't change this at all and going by our page for
Pocket Reality Manipulation, it's explicitly layed out that this power revolves around
manipulating and creating pocket realities. A black hole is
not a pocket reality. Absorbing/Creating a black hole does not qualify for Pocket Reality Manipulation at all. (Also not sure if Sera's a reliable source anymore considering the stuff she pulled)
Buu's absorbtion =/= Mechikabura's absorbtion. Gaining a new piece of clothing is not even remotely comparable to gaining a new part/extention to your very
physical being. While it's true that Buu gained some attributes over absorbing the Z-fighters , that doesn't make it the same as Mechikabura absorbing the black hole as there are clear differences.
Also I'd rather not bring up other verses here since in most cases there is completely different context surrounding them. Kirby has his own feats, statements and physiology and they should just stay as such.
Also the notion that Mechikabura has some "portal" to the black hole sounds extremely weird. The black swirly thing on Mechikabura's chest is very clearly meant to represent the black hole that he just absorbed (You can literally see him placing the black hole on top of his chest, instantly transforming after that). It became a part of his body and we can see it on his chest after Demigra pulls the Time Patrol out from Mechikabura's black hole. Simple as that. The black hole being in his chest debunks the notion that he just "compressed it" inside his body as it's very evidently depicted as a literal part/extension of his physical body
Edit: I'll wait to see what Ultima says