@jhaas that's also true. There are third party commercial services that try to do that (coveragemap.com, etc., though they just let you choose between the FCC map and maps built from user-submitted data they called the "verified map", which is even less complete...ideally they'd be merged), but there's no public data source that I can find.
I mean, it's good that the government requires vendors to provide these maps. And, I guess it's good they're seemingly not exaggerating, in my experience.