Your thinking that the “tap, hold, wait” friction was intentional is right on. It’s exactly what came to my mind after reading the first paragraph of your post.
I would consider 50 claps using your interaction less “valuable” than 50 claps with Medium’s current interaction simply because it takes longer for the user.
The mobile/desktop clap rate difference is a big issue that medium needs to resolve immediately 😬
I had no idea about the undo function in the share action sheet!