The article cites that Lego itself has noticed, through empirical testing, that the two groups (statistically speaking), use the sets differently.
The critics, through virtue of their assumptions about how gender equality should work, seem to imply that this distinction isn't there and everyone should be happy with the same set.
So let me ask this: if there really is a difference in play styles (exterior versus interior focus on the set, for instance), why wouldn't you as a toy maker design two lines of sets - one with a focus on interior details and one with a focus on exterior ones?
If you try to combine it, for the price point, the toy is going to be slightly weaker for each segment of the population - effectively raising the price on both groups to have the toy they actually want by mandating we must have one toy in the name of "equality".
Seriously, can someone explain what's wrong with two lines of toys if Lego (through testing, no less) has found that there are two distinct groups of wants?
No one would suggest that if it were boys split in half in their interest of interior versus exterior, Lego would be remiss in offering two product lines, so it strikes me as incredibly... insecure about gender equality, to the point of pathologically insisting there be no differences, to say that we shouldn't have two lines because of the divide happening mostly along gender lines.