I'm well aware of that thread, as I've owned the Mini since they launched it in Nov of 2018. I never bothered to read it when it was created, or now, as I never had any issues with mine. Keep in mind, people who post on forums about computers probably make up less than 5% of actual owners of said device.
As far as the Mac Pro, I can't say I've tried to pair a bunch of things all at once. I don't game on my Macs, nor do I use bluetooth headphones. About all I pair via bluetooth is my keyboard and mouse. I would imagine if you're trying to sync multiple heavy use devices at the same time on a 10+ year old computer, you're going to have a bad time.
As far as the Mac Pro, I can't say I've tried to pair a bunch of things all at once. I don't game on my Macs, nor do I use bluetooth headphones. About all I pair via bluetooth is my keyboard and mouse. I would imagine if you're trying to sync multiple heavy use devices at the same time on a 10+ year old computer, you're going to have a bad time.