What do you mean by "pure signalling"? You evolve to show the signal. Whether the actual metal process that makes the signal is a cost-benefit analysis on lying or actually believing what you say doesn't matter. Does evolving to automatically feel more empathy for children as a way of signalling that you'd be a good parent count as "pure signalling"?
As per a recent comment this thread is meant to voice contrarian opinions, that is anything this community tends not to agree with. Thus I ask you to post your contrarian views and upvote anything you do not agree with based on personal beliefs. Spam and trolling still needs to be downvoted.