[css-multicol][css-flexbox] column-fill + flex

I don’t usually relay my personal CSS frustrations to this list, but I think I might have stumbled on a spec bug (and if not, certainly on a browser bug) and I’m not familiar enough with the layout specs to exhaustively check which of the two it is. Check my reduced testcase here [1] in both Blink & Gecko. There are several issues there:

1. column-fill is not applied when the height is controlled via flex, but only if set explicitly in an absolute unit.
2. When no height is set, Gecko is not applying multicol whereas Blink is (just without column-fill: auto).

Am I missing something here? I don’t see any such restrictions on [2].
In any case, I thought the use case could be of interest, as I don’t recall many discussions about the combination of multicol & flex.

Cheers,
Lea

[1]: http://dabblet.com/gist/5f52a72c57c632905757 <http://dabblet.com/gist/5f52a72c57c632905757>
[2]: https://drafts.csswg.org/css-multicol-1/#cf <https://drafts.csswg.org/css-multicol-1/#cf>