Horizontal list space between items not working

Even in the demo presented by Antti you can see this problem.

I was about to ask about this and I was suggested this topic when I was writing the subject. I see the horizontal spacing between items in a horizontal list only works for some sizes. Here I add two screenshots, in one of them it is working but if I use a wider window, it does not work:

Thanks for the reports! The issue is now fixed for the next release.