Ultimately everyone who uses the beta is volunteering their time and engaging with it at a level that works for them for reasons that make sense to them. For some, it's because they appreciate the product and want to help improve it. For others, they just see it as a preview of the new features they get because they use this forum.
In a private beta you choose your participants and set expectations and have a one to one agreement on what the purpose is. In a public beta you give up that specific control in exchange for volumn. You hope that through quanity and variety of users stuff will bubble up that your smaller, specilized private beta might not have found. You might get the uninformed user who has no idea what something is supposed to do using it in an unexpected way and finding a bug. Though sheer quantity you get a few users reporting issues with the 5150 models that more dedicated testers or staff can explore. You give up the micro-level control to hope that things average out to useful on the macro-level.
It's fine to offer suggestions on how people who have problems can dig in further to confirm or invalidate their experience, but everyone is on here for their own reasons. Don't blame the user complaining about the change in sound for reverting, he isn't a software developer, prodect specialist, or quality assurance staff at fractal. He's a musician wanting to make music, and reverting to the previous release made more sense for him.
He also likely encouraged some of the more didicated users as well as fractal staff to look into it, so it still got chased down even if that user didn't want to engage with it anymore.