[css-transforms] CSS3D breaks with opacity flattening

The following is a big problem for people making 3D scenes, and I really
think this needs to be rethought:

https://bugs.chromium.org/p/chromium/issues/detail?id=646993

Not only does it break existing apps, but it also makes it difficult to
create 3D HTML scenes that involve opacity. The intuitively expected
behavior (as listed in that issue) is that opacity applies to children but
does not cause unintuitive flattening.

If browsers follow the latest spec, then we are making it more difficult to
do and discouraging 3D in the web, which I don't think is what we want.

The faulty part of the spec is here:
https://drafts.csswg.org/css-transforms/#grouping-property-values

It states that opacity should cause grouping, which is what causes the
flattening.

Is there an alternative way to achieve opacity less than 1.0 without
flattening of 3D scenes, that I may have missed? Unless there's an
alternative, this behavior is a bad idea for authors of 3D HTML scenes.

*/#!/*JoePea