I noticed this some months ago. My local Three mast that I usually connect too, has for the past 18 months connected to primary upload band 3 and showed it as 4G+. This 1800Mhz cell, 2899202 is one of 8 cells located on the tower operated by Three. Then around 2-3 months ago when establishing a connection, it would no longer automatically connect to 2899202 for the primary upload and instead began to use 2899208 which is a B20 cell, yet this still showed as 4G+. Needless to say the speeds on the B20 band are pretty poor and there is clearly no CA even though it displays the 4G+ status, so since this time I have had to use H-LTE to force band 3 for upload, which now only shows as 4G. Band 3 is pretty heavily contended in my area as Three only have this one mast locally. IMO it appears that three have tweaked things, probably to try and direct traffic onto the B20 cell to alleviate some congestion on Band 3. I suspect they have done this at several locations, in an attempt to balance their questionable network infrastructure.