The join is designed to keep you in the holding protected area just like the hold pattern proper, so you may descend to minimum holding altitude once there (if so cleared by atc). You may also go straight into the procedural approach from the join without flying a full pattern - the join and the hold are the same. That's how I understand it.....
I'd be stuck if I had to quote you a reference, though. I'll have a look around and get back to you if I find one..... (don't hold your breath!!
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