Yeah, I'm not too sure about the maturity thing either, but I do have male toads that seem a little too young to breed yet they squeak all the time when picked up. I'm not sure if sexual maturity needs to be reached since it's a non-breeding call. It's basically an "I'm a male so get off me" call.
https://www.youtube.com/watch?v=ifq7d18EgGE