[css-anchor-position-1] Compensating for scroll & "as if affected by a transform"

[dshin-moz]

Spec says:

After layout has been performed for abspos, it is additionally shifted by the default scroll shift, as if affected by a transform (before any other transforms).

What's the extent of "as if affected by a transform?"

Does it establish a containing block for all descendants?

e.g. If a scroll compensated positioned element has a fixedpos frame inside it, does it get trapped inside the positioned element?
Both Blink and WebKit does not seem to do this - The fixedpos frame's containing block seems to be the viewport. asfia.html

Does it have the same overflow behaviour?

e.g. Does the ink overflow caused by the positioned element affect its containing block's overflow?
If the abspos containing block has overflow: scroll, and a positioned element compensating for scroll overflows it, but then the anchor's scroller moves so that the positioned element no longer overflows the abspos cb, does its scrollbar shrink?

Both Blink and WebKit seems to keep the overflow constant positioned-overflows-abscb.html
OTOH, when this is emulated with JS + transform: translateY(), the overflow changes positioned-scroll-emulate-transform.html

[dshin-moz]

Test case that avoids the effect of overflow from the initial(Previous spec behaviour)/remembered offsets, using direction: rtl: anchor-scroll-rtl.html

Overflow of the positioned element shifted by scroll does not seem to contribute to the scroller size at all.