Cell Towers may or may not show depending on the source you're looking at. I've seen "stealth" cell towers that won't have an ASR registration (things like flagpoles, water towers, church towers or even fake trees). 5G sites are even worse, hiding on power poles and other inconspicuous places. Likewise, some traditional sites are leased and won't show the carrier name registered to it.
When looking at availability of cell coverage, you're better off going to the carrier and looking at their maps (for T-Mobile, check out their
5G & 4G Coverage Map) - if you remember those old TV ads "Can you hear me now? Good!" all the major carriers actually do have testing campaigns that measure their coverage like that (albeit much more automated than the commercials depicted, but they are driving around much like Google Street View does) and work hard to keep their maps up to date.