[css-flexbox] Firefox+IE absolutely-positioned bug?

It seems that both Firefox and IE have a bug with absolutely-positioned
items.
The spec is hard to grasp for absolute items, but in any case, there is a
discrepancy with webkit.

I am wanting to use an absolutely positioning flex item on mobile
as fallback with -webkit­box and -moz­box for their lack of flex-flow
support.

So for example, I have vertical flex items [ABC], with [B] and [C] at
'order: 10',
[B] at 'order: 1' and  [A] set to 'position: absolute' with 'top: inherit'.

The way webkit behaves is that [A] absolutely-position below [B] with top
either set at 'initial' or 'inherit',
and acknowledge the reordering step of [A] now in second position (after B).

If I set 'top' with a value,  the 'top: 0' basis of [A] is the top root of
the flex wrapper in all browsers.

What is the correct behavior for 'initial' or 'inherit' in this
circumstance?