Earlier quoted context omitted.
Virtue signalling is not about being virtuous. The other, much more important part, is the signalling. The impulse of companites/people/etc to brag about being virtous only to appear in a better light. A bit like vegeratians who often can't resist the temptation to tell the world that they're better.
Yes, at the core of the "virtue signalling" philosophy is the idea that nobody _actually_ holds virtuous values. There are only two kinds of people: those who are honest about being selfish jerks, and hypocrites who disguise their selfishness using "virtue signalling". It's reminiscent of the psychopath world-view, actually.
No, lucozade put it well: Being virtuous is unrelated to saying you are. That does not mean that saying you're virtuous means you are not. Simply that there is no causal connection.