Surprise! I always thought those were sealed. FTW
Considering how they intended these to be used, I wouldn't worry too much about it. Also, for Rears and Atmos speakers, one doesn't need to fret about matching things up and completely playing by the rules so much...
Having said that, yes, it is important to do what we can, when we can to honor proper set up, in terms of placement and implementation... but these channels are generally less stringent than the Front 3 and even the Surrounds.
Towards the idea of proper placement and Implementation:
Rule of thumb is that the distance from a wall should be twice the diameter of the port.
Atmos and Rears do not need to match each other, much less the mains. It is nice to get similarly voiced Speakers. Ideal to match everything. But necessary?...not really.
I leave Surrounds in a little bit more nebulous category. To me, being interested in Multi Channel Music (5.1 Audio), I put much greater emphasis in my system on having great Surrounds and matching Amplification. To many, though, Surrounds can be treated much the same as I described Rears and Atmos...
All that said, the individual setting up their system has to be responsible for identifying where their values lie in terms of the importance given to the various Speaker choices and placements. Perfection vs Compromise, Quality vs Quantity, etc.
