[css-transforms] rendering 3D-transformed sibling elements without preserve-3d

Consider example 7 here:
http://dev.w3.org/csswg/css-transforms/#3d-rendering-contexts

AFAICT this doesn't match what Chrome and Firefox do (can't test IE). In
those browsers, sibling elements can't intersect each other unless
preserve-3d is involved somehow. In those browsers, in the absence of
preserve-3d, 3D-transformed children are transformed, projected and
composited in regular CSS order. I suspect that changing that will create
major Web compat issues.

Or am I misunderstanding something?

Rob
-- 
oIo otoeololo oyooouo otohoaoto oaonoyooonoeo owohooo oioso oaonogoroyo
owoiotoho oao oboroootohoeoro oooro osoiosotoeoro owoiololo oboeo
osouobojoeocoto otooo ojouodogomoeonoto.o oAogoaoiono,o oaonoyooonoeo
owohooo
osoaoyoso otooo oao oboroootohoeoro oooro osoiosotoeoro,o o‘oRoaocoao,o’o
oioso
oaonosowoeoroaoboloeo otooo otohoeo ocooouoroto.o oAonodo oaonoyooonoeo
owohooo
osoaoyoso,o o‘oYooouo ofooooolo!o’o owoiololo oboeo oiono odoaonogoeoro
ooofo
otohoeo ofoioroeo ooofo ohoeololo.