This holds true for youtu.be links, but not youtube.com/watch?v=
Discord file url parameters are to prevent using discord as a free cdn. I believe discord plans on actually enforcing expiration later this year or early next year, at which point those extra url parameters will actually be necessary (and the links will no longer work indefinitely)
By the way for anyone who doesn't know, the ? only appears once in the url. Successive question marks are instead denoted by &
For anyone wondering, their account was created two days ago and half of their handful of comments are like this. That person is baiting. Just report, block, and move on.