Remember, mathematically, a blackhole is mass in an infinitely small point. You are dividing by 0. I don't know the answer, but if someone is saying that from the outside the apparent mass is different than from the inside, that doesn't set off any alarm bells. We literally are talking about Dr Who style "it's bigger on the inside". Even the ladder example should make you think about mass. Without relativistic effects the mass inside the barn is only part of the ladder. With relativity, the whole ladder, and thus mass, is inside. So yeah, weird things happen.
Things don't get more mass, they just take more energy to accelerate which looks a lot like more mass.
It doesn't imply for example, a high speed mass would cause more gravitational attraction than a slow one.
If that was the case, a black hole would be even worse as it accelerates matter towards itself and it gains "bonus mass"
Unless the theory also breaks mass and information conservation, the star that gave birth to our black hole must have been as massive as our entire universe.
I doubt we have any theory how a star that size can have formed.
>> Yes and no. You're not thinking about contraction. With relativity >> we can fit a 100ft ladder inside a 10ft barn.
I believe the OP was talking about mass, not linear dimension. (And if he wasn't, I am.) Unless somehow mass inside a black hole is not constant? (ignoring accretion)