How would you not block debuggers if those aren't verified? This adds insane busy work for little advantages and again would make Microsoft the gatekeeper of hardware.
For which benefit exactly?
There are no problems with debuggers. For one, debugging an app that isn't compiled in debug mode is very hard. If you're at that point something has gone badly wrong somewhere already. For another, there would only be a problem if you're trying to debug a production build of the browser whilst simultaneously accessing a service that wants to measure your environment. That would be an extremely specific scenario that virtually nobody would ever encounter, especially not compared to the much more common scenario of being asked to solve horrible CAPTCHAs.