...which means that describing an act as "signalling" is basically meaningless, insofar as it fails to ascribe to that act a property that distinguishes it from other acts. It's like describing my lunch as "material". True, yes, but uninteresting except as a launching point to distinguish among expensive and cheap signals, forgeable and unforgeable signals, purely external signals and self-signalling, etc.

That said, in most contexts when a behavior is described as "signalling" without further qualification I generally understand the speaker to be referring more specifically to cheap signalling which is reliably treated as though it were a more expensive signal. Hanging out with mathematicians and adopting their jargon without really understanding it usually falls in this category; completing a PhD program in mathematics usually doesn't (though I could construct contrived exceptions in both cases).