I started a new job last year with 10 days of vacation. It wasn't until December that I learned that five of those days were mandatory for the week between Christmas and New Year's. If you had no vacation days left, it was unpaid time off.
Being clear about this with new (and especially young) employees is a good idea as to people straight out of college, it's not obvious.
But there's certainly nothing dodgy about it.
But it's 50% of his total time off. Is that "the norm"?
On the bright side, if you take a five day vacation and bookend it with two weekends, that's a nine day trip.