Signalcheck's CA reporting seems to be much more accurate with my P4XL than my old P3aXL that I was using off and on - at least on AT&T. Obviously it is still early - I have only had the P4XL for about 27 hours, but so far so good.
With the 3aXL, I would keep seeing values getting stuck and it showing CA active where I live even though AT&T only has a single 5x5 B12 carrier at the moment. Hasn't happened once so far with the new device.
Yeah, I've seen a huge expansion of Massive MIMO. The original DC 5G area shown earlier in the year was basically from SW DC to Tysons. But I went to Baltimore over the weekend, and there's now Massive MIMO around much of the beltway, and then I spotted two Massive MIMO sites in the Baltimore market. There was also two more sites south of Woodbridge on I-95 the weekend before, one of which was in the Richmond market.