Good observation.  To a degree, the answer is yes.  

I say to a degree, because the danger will come into play more at higher edge angles.  We do have some ability to hip angulate when skiing square.  It's done by flexing sideways at the waist.  The trouble with that is, the range of motion we have when flexing sideways at the waist is rather limited, so we can angulate only a small amount.  Because lower edge angles require less angulation to stay balanced on our outside ski, we can get by with it there.  However, as edge angles grow, we need more angulation than flexing sideways can provide, so we're forced to supplement with knee angulation to remain balanced on our outside ski.   To get that extra angulation we have to counter our hip, so forward flexion actually angulates us my moving our Center of Mass towards the outside of the turn.  Because we have a much greater range of motion when flexing forward than we do flexing sideways,  counter provides more potential to angulate.  Just what we need as we move onto a higher edge angle. 

Skiing square is fine for steered turns, where low edge angles are the norm.  When steering, too much counter can impede our ability to be strong and precise.  Square is also a good rotational state for skiers attempting to shed their pivot, and learning to initiate their turns cleanly, with no tail push.  But in general, a good approach is to begin a turn with just a little pelvic counter.  Just enough to pronate the outside foot.  It doesn't take much.  From there, simply add more counter in harmony with the increase in edge angle.