This is not about having bitcoin as a reserve, this is not about using bitcoin as a national currency neither. This is about having a national fiat that is backed by bitcoin which is very important for nations to have, not just bitcoin but something to back. Otherwise you will become like USA that prints money out of thin air and has no backing aside from the power of USA government and that's it.
One day if USA becomes not so powerful (which looks like may happen sooner than later) people may reject accepting dollars and will start taking euro or yuan or whatever is strong at that moment and that will destroy the american economy beyond saving. In order to stop stuff like that from happening countries should have something backing their fiat, it could be bitcoin, gold, silver, oil or whatever they want.
I think that we will have to come to terms with what the state is doing and will continue to print their money, just like dollars from the air. History has already shown that using gold and silver in everyday life is fraught with so many problems. Of course, cryptocurrency solves a lot of problems, but we must understand that not everyone on the planet can use cryptocurrency as a means of payment. As for Bitcoin, the actual use of it all over the world is already losing its relevance, since each country can afford to create its own national cryptocurrency, with a limited number and with better technical characteristics than Bitcoin. but it is likely that Bitcoin could become an international cryptocurrency.