Which they can only do for unencrypted traffic, encrypted traffic by definition would not be examinable by the FCC for determining whether to assign fines.
They don't have to know what you are sending to know you are sending in a way you shouldn't. It's not even about the content of the encrypted traffic at that point. They just see broadcasts (which...good luck hiding them from the FCC) and if they see the bandwidth being used but aren't receiving a usable audio/data stream from it, it's really easy to tell if the rules are being followed.
Is the band you are transmitting over restricted in any way? If they say no encryption, it doesn't matter what you are encrypting. If you are caught broadcasting in that no encryption band, and they see broadcasts in that band that don't correspond with signals they can pick up, it's a red flag that it's encrypted traffic.
Think of it this way - hypothetically if I'm on an English only band, and it's illegal to speak Spanish because English speakers can't understand Spanish, and I get caught transmitting anything other than English it doesn't matter what the content is.
Encryption doesn't magically make the RF you are using invisible. It makes it unreadable. It's still broadcasting and can be picked up by sniffers that flag it as data it can't interpret. It is NOT a no-risk choice.