Meh I was only citing regulation.. Not what was the better answer. Like I said.. Never had to bury a joint in a wall soo..There will be 101 better ways to do it like MF JB in the ceiling under the floor or even a screw type JB in the attic. Personally when I stick a JB anywhere even if it’s MF I like to make sure it can still be accessed even if there is no requirements for it to be I’ve seen “wago type” connectors either knock offs or other legitimate brands fail spectacularly, so even with MF it probably isn’t the best of ideas to make it totally inaccessible.