I believe that's it. The topic of coupling or uncoupling drivers gets very quickly to: What problem are you attempting to solve?
You want a good seal. You don't want loose bits vibrating (buzzing), or a resonating frame (or cabinet) sucking energy away at frequencies you want emanating from the cone.
How that gets solved (mass, bracing/stiffness, dampening material(s), ...) is a system designers job to take seriously or ignore, and less a yes/no question.
In this case, unless you're using unconventional construction methods or materials (in which case, you're on your own), I'd humbly suggest either going with the nominal JBL driver attachment method or experimenting a bit, perhaps with a thicker baffle and/or bracing from a stiffened rear panel to the back of the 2216 (can get complicated quite easily, but with DIY, the sky is the limit
). Of course, you may end up with a box that has horrible resonant modes if you're not careful... Hence the known recipe suggestion. Very nice driver, BTW.