The horror, the horror

I don't disagree with the facts as you state them at all, I was just pointing out why being a TMO member might not make one more likely to be selected in the beta group, perhaps even the opposite.
If you're beta testing for obscure bugs in your main OS, then don't select users who are likely to be (a) more interested in some other OS, and (b) preconditioned to not be bothered by minor bugs in apps (because they are entirely used to nothing being quite ready for the big time).

And as for your last point, well, I will have to plead guilty as charged