I am not a doctor by any means, but the information they have given you sounds so off to me. Are they knowledgeable about trans people at all? Or is this a general hospital?
What they said about closing it up is just not true. If it were, I wouldn't be able to pee right now. What is true is that it is a risky procedure because so many delicate things are near (like the urethra). But other than that, it can be removed.
Also, the hole closing by itself sounds odd to me too. This would mean that females who do not have sex, or use feminine products that go inside, would also have their holes closed up after a while? Sounds highly unlikely to me.
The answers they gave you raise a red flag to me, but again, I am not a doctor nor an expert.