group isolation and filters

All, 

do people believe that filters should cause groups to be isolated?

I've attached an example how this affects rendering. The example is a group that contains a blue and a green rectangle that is on top of a red rectangle.
The green rectangle has a blend mode attached to it.
In the last graphic, the group has a filter effect applied to it.

My question is: what would you expect the result to be?

Rik