You know, in your case my gut feeling also says it’s related to macOS and that specific mini rather than the hardware. Perhaps there could be something wonky with the T7’s bridge circuitry, but my money really wouldn’t be on the hardware, especially the cable.
But that said, I’ve become increasingly weary of cable issues. Not long ago I went through a massively odd ordeal trying to get a simple USB-C connection to work using the manufacturer’s included cable, which was neither faulty nor flimsy, and definitely not cheap, and I just couldn’t get things to work. Tried many other quality USB-C cables and nothing worked out. Finally, in an act of despair I tried Apple’s expensive 80-cm TB3 cable and low and behold that did the trick, all oddness went away. NB, this was a USB connection, not TB. And ever since I’ve felt that when you have a kind of odd issue with connecting hardware, especially over USB with all its complicated variants and overly confusing spec terminology, you can’t really try enough cable alternatives and variations. Of course this is assuming you’re curious to truly wrestle this issue to the ground. Otherwise, it’s likely mostly a waste of time. ;)