I refuse to believe there exist two pieces of software that are truly for all intents and purposes identical, unless one is a very recent fork of the other.
Both Lemmy and Ladybird are very pointedly not forks of anything.
Which is unrelated to their point, which is that visible popularity of a piece of software (e.g. having many downloads in an app store) has a large impact on likelihood of people to trust it.
You feigning ignorance at this just discredits your own position. Their question was essentially rhetorical, and you chose to answer it incorrectly rather than concede their correct point:
If you encountered 2 identical pieces of software, you would trust the one that is more popular, thus proving that popularity is a meaningful benefit to a piece of software.