...and sometimes when he just forgets she's there, like at the beginning... but this is usually what I come back to unless he was napping when I snuck away for a minute to make tea or visit the human litterbox... And he just gets so involved in chewing the gate that he sometimes forgets to stop even when I get back.

Yes, UnBun has an enclosure, he likes the taste of wood, upholstery, carpeting, wires and pretty much anything else he can get his teeth on far too much to be freeroamed unsupervised. His enclosure is most of the living room, he's got plenty of space and most of the stuff in it that he likes to chew on has been covered with stuff he doesn't like to chew on. He typically uses one corner of the enclosure to throw hay around and sleep in, when he doesn't just retire to his crate after his daily ~15 seconds of zoomies...