Yes and? If you carry this on your keychain heading into a security checkpoint, expect to receive interrogation++.

So how long do they interrogate you before deciding there's really no hidden volume? And even if you do reveal a hidden volume, how could they ever know it's the only one? It's pointless, even if they know about the technology.

It really much depends on the individual case. In a constitutional state it should make a difference if obviously an encrypted volume is used or if there is the possibility but no certainty of one, two, three or four hidden volumes.