Speaking from experience, the MBTL was not of any use, or barely, when I was trying to find beta testers for ARPIA2. I knew what I wanted: one or two very knowledgeable WinNova users (I got slouch and Belthazar, probably the best in that field, at least at the time I'd known about the two of them since a topic in the EVDC concerning the fact Arpia1 didn't work on WinNova, due to the interface size), and a few other testers. In the end, for the "few other testers", I sent an e-mail or a PM to those I'd known personally for some time ("personally" basically, people from the Kontik Research Front) or to those I knew were very good at nitpicking. And I ended up only getting one new beta-tester, among those: Guy.
Three beta-testers found via ASW, no use of the MBTL.
But I wasn't disappointed, not in the least: in his week of testing (we thought we would get the new ship graphics in that very same week, but in the end, we had to wait a few more months), Guy found out a gazillion spelling/logic/ mistakes, and came up with a gazillion other suggestions. When Belthy & slouch had been on the case, they'd also found masses of things to point out.
Then you can add less important testing (but still useful) by the people who contributed to ARPIA2, most notably by insomniac.
And then, when you add my brother's testing and my own to the list, it made up for a pretty solid basis for release.
So yeah, that list wasn't all that useful. Not to me, at any rate, and I'm sure I'm not the only one who proceeds/proceeded that way.