The author used Tinder as an example of “signal amplification”, in that, a method to reach more people. So the signalling on Tinder is your profile - pictures

The author used Tinder as an example of “signal amplification”, in that, a method to reach more people. So the signalling on Tinder is your profile - pictures and description, they monetise the ability to signal to more people. And, as you alluded to, they absolutely don’t make that action public since amplifying your signal on a dating app reeks of desperation.