I also find it strange! Simba 5G is quite wide on that map but somehow not many people or phone models can get the 5G even within its 5G coverage spots.
Simba using 5g NSA which built on top of 4g cell. In the cellmapper map, u can only see n40 cell but don't know if they are 5g or 4g.
Only nperf map can see trail of 5g coverage contributed by users.
Phone wise I think if your phone have 5g NSA n40 band, u should be able to connect. But 5g range probably shorter and not easy to get.
Very sad that 5g development are slow due to us-china tech war. Stopping Huawei from expanding.
Telco are also hesitating to upgrade their infrastructure to StandAlone tower and getting from the more expensive Ericsson/nokia devices.