I am not aware of a single Maxonian moonlighting as a Betatester. Of course we all participate in testing and reporting, but this is not an extra effort but part of our work. We do have an internal team that does structured testing, but our Betatesters are needed to test in real world scenarios. You can't make up for that in house.
The number of issues reported is not a reliable indicator. Especially reports from the public are often based on other issues than actual bugs, more often then not user errors, where reports can be useful as well just not as bugs, or other unrelated things.