Wtf is the point of “Unlimited PTO” if I can’t, in fact, get unlimited PTO

I requested PTO at my job for a month to travel and see family after being severely burnt out (while covering for my manager while she was out on maternity leave), and she denied it saying that it would be “too long”. So now I’m still going for a month, but only got two weeks approved and have to work during my vacation for two weeks. So ridiculous it makes my blood boil