"It's only popular, it's not really central to F-Droid itself."

I've used F-Droid for years and I've never used the client ("the F-Droid app")

For me the value of F-Droid is as a list of open-source software with (a) pointers to source code and (b) sample binaries

The goal of F-Droid could be to enable Android users to read, edit and compile the software they choose to run on their "phones"

But F-Droid promotes their own app ("the client") so maybe the project's goal is something more like an "app store"