I wonder if the Mini 6 has the new Qualcomm modem or the one from the iPhone 12 line. I guess the latter. But I always get way higher speeds on my iPad mini 6 as to my iPhone 12 mini. Maybe it is the antennas.
I was in a city in my home country, we don't have that good 5G coverage yet. Mini 6 got 450-500 most of the time when my iPhone 12 Mini got 200-350 at the same time.
I need to put the Mini 6 through a test while traveling through countryside with annoyingly bad reception but from first impressions it has very good reception.