I agree! It is a feature to make the user interface simpler and easier to access without actually switching to the app. By that logic a tap should do just that i.e. expand the Dynamic Island and allow the user to control the music or whatever without switching to the app (somewhat of a multitask or apple's version of it). A long-press or a double tap (or maybe another tap after the DI expands) should take you to the app which it does, as that is when I would like to get more options not present on the DI.

For example, you are driving somewhere with music on Spotify and using maps for navigation. The DI is looking all nice and pretty with its colored waveform but you quickly wanna skip the next track in the playlist. What would be the easiest way to do that?

A. You tap on the Dynamic Island, it expands giving you the controls, you skip the song and job done.

B. You try to touch and hold the Dynamic Island for which you have to hold your breath and keep your finger on the same spot which is a challenge and if there is a slight bump on the road, your finger moves on the screen and then you have to repeat the process again which is a pain!!

For me, the tap to expand and long-press (or even double tap) to take you to the app would make much more sense. I do know that apple fangirls would say that it is consistent with the rest of iOS or to treat it like a notification panel or whatever, but I really don't care about that if it makes things more difficult.