Bug? page breaks in epub

Some days ago, I asked how I’d get page breaks within chapters into my epubs.

Now I think, it’s sort fo a bug that they don’t show.
Because: I made a mobi file and there they were just fine.

Then, with my old calibre I converted the epub2 from Scrivener to an older epub2, because tolino can’t handle the “newer” epub2.
And there, in that “old” epub2, the page breaks were present and working, too…

So now I think with epub3 and the “new” epub2 something must be wrong.