You've basically come up with four criteria that describe the use of the word "signal" in a highly specific context - traits that exist for pure signalling purposes in evolution or game theory - and then decided, arbitrarily, that this is the one true meaning of "signal." I do not think you have provided adequate evidence or argument to back this claim up.

Aren't you arguing over definitions here? If he had defined a wholly new term as having that meaning, would your objections still apply?