Compressing compressed contents

First off, a really big thank you for making it possible to distribute my Mapton application in this way.

Having published my first attempt a while back, it’s now time to make an update.
While playing around with appimagetool and jlink regarding compression I noticed that the more I compress my Custom Runtime Image produced with jlink the larger my AppImages get, with both gzip and xz.
-c ={0|1|2} or --compress={0|1|2}

Enable compression of resources:

* `0` : No compression
* `1` : Constant string sharing
* `2` : ZIP

How is that?
I guess one should not include compressed stuff if possible.