[css-view-transitions-1] What's the point of position: fixed in `::view-transition`?

[emilio]

https://drafts.csswg.org/css-view-transitions-1/#snapshot-containing-block-concept says:

The snapshot containing block is considered to be an absolute positioning containing block and a fixed positioning containing block for ::view-transition and its descendants.

Then https://drafts.csswg.org/css-view-transitions-1/#ua-styles:

:root::view-transition {
  position: fixed;
  inset: 0;
}

but afaict that position: fixed is just confusing, and behaving exactly the same as position: absolute, since the snapshot CB is a position: fixed containing block, right?

Should we change it just for clarity? Is it just an historical artifact?

cc @noamr @BorisChiou @vmpstr