Hey! I'm Henry, one of the engineers working on Mo. The approach to testing itself is very similar to UAT, except that it's fully automated. This means you can speed up the feedback loop significantly. Imagine instead of having to wait for the next release and run a time-consuming manual bugbash in order to find out that your changes broke something, you can get feedback immediately on any PR you want, at a fraction of the cost.
The fully automated feedback on every PR is the useful part, but a bug-hunting agent needs its own measurement. Plant a handful of known defects in a staging copy of an app, such as a disabled button state or a wrong total after a coupon, and check how many the agent reports across repeated runs on the same build. If it finds a defect one run and misses it the next, the run-to-run variance matters more than the headline catch rate. I'd also want it to report false alarms separately, so a reviewer can see how much time each PR comment actually costs.