That is really weird.

Yes, peole do clap without reading. Even if they are friends, and even if they say they did read you.

What the algorithm does is check that one scrolls slowly down the screen. That way it knows it is being read. I think one only needs to be read for a few seconds to be recorded as a read. I don't think it makes any difference whether one clapped first or last. At this point in time, claps are a vanity exercise. They don't mean anything to the algorithm, I don't think.

One of the reasons it is a good idea to publish all one's stories in one's own magazine is that it gives you the amount of time people read. So there can be no mistaking whether the piece was actually read or not.