If your phone shows “5G,” you’re not necessarily connected to the latest and zippiest cellphone network technology. It might just mean that 5G connections are available nearby.And the bars are a cellular version of a shrug. There is no standard measure of how much signal strength each bar represents.
I'd kind of figured out the latter (or at least, I knew that it was murky), but had sort of assumed that if my phone said I had 5G, I had 5G. Good short piece on what actually happens when we make cell calls.