We're talking about downloadable software here, not a cloud service like google. Once a hostile nation state has access to your binaries (as they would with an installed product like A-V) they can just fuzz the A-V detection method to find bypasses.

Heck that's what pentesters and red teamers do on a regular basis, A-V bypass is a common thing in that world, so if people at that level can do it you can bet that nation state actors can do it.