When I see these articles, my first thought is, how are they so certain that they aren't getting chatter from classified satellites? e.g. X-37 flies an erratic

When I see these articles, my first thought is, how are they so certain that they aren't getting chatter from classified satellites? e.g. X-37 flies an erratic mission profile, which could completely explain the intermittent nature of their signals. Who's to say there aren't undocumented higher orbit spy platforms? Radiotelescopes are necessarily large and, afaik, all terrestrial as a result.