I've never heard that theory. I have heard folks say that the smoke ring will stop forming at around 140 degrees, but never anything about the pit temp.
Here is a brief article about the smoke ring formation...
I haven't looked into the science behind that, but it seems to make sense.
So, have a lower pit temp will keep the meat below 140 degrees longer and should theoretically give a better smoke ring. It will also take longer to cook, so the meat will be exposed to more smoke.
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