While on their blog to take the final quote, I found the found UI progress report that I missed when it was published: https://puri.sm/posts/librem5-progress-report-4/

There are more details on the homescreen at the end of the post. So I have now found where the application launcher is ! It is below the homescreen, a bit like on Sailfish OS 1.0.

And interestingly, there is this sentence: "Less recurrent gestures, like accessing the settings or the detailed list of notifications, are available in the upper part of the screen."

So I guess I found where a part of our disagreement in the UI comes from !