Unless there are contradictory responses from others, I usually don't comment when someone gives a solid answer like Cold Fusion did. In this case, the only thing I would add is that, if a coupling were permitted, then a seal wasn't needed in the first place. See the various Exceptions for boundary seals in 501.15(B)(2).
There is one case though where a seal might be beneficial, but not required. See 501.15(B)(2) Ex No 3. I noticed the OP mentioned the boundary was a block wall. I am assuming the unclassified side of the wall is the interior of a room. If the room was unclassified by virtue of pressurization, then a seal may be useful to help maintain the pressure. In that case, a coupling between the seal and boundary would be acceptable, but only because the seal wasn't required in the first place. This is especially true since Division 2/unclassified boundary seals are no longer required to be explosionproof.
