Than X versus Than are X

[JustinC279]

from CAT exam:

Independent contractors pay higher taxes and paid less consistently than are statutory employees, but they, unlike statutory employees, are freely allowed to perform the same type of work for multiple businesses.

A: taxes and paid less consistently than are statutory employees, but they, unlike statutory employees, are freely allowed to
B: taxes and are paid less consistently than statutory employees; unlike statutory employees, though, independent contractors are free to
C: taxes, are paid less consistently than statutory employees, and, unlike statutory employees, they may freely
D: taxes and are paid less consistently than are statutory employees; in addition, unlike statutory employees, independent contractors can freely
E: taxes and paid less consistently than are statutory employees; moreover, unlike statutory employees, they are allowed to

I narrowed it down to B and D correctly based on parallelism X AND Y.
However, I got confused by the Y portions of both.
Of course, another major differentiator other than that is that B has the correct meaning of contrast after the semicolon whereas D does not because "in addition" is not a contrasting shift.

B: pay....and are paid less than statutory employees
D: pay...and are paid less than are statutory employees

is 'than are' incorrect?
Is it supposed to be a comparison idiom that I should know?

Thanks!
Justin

[Sage Pearce-Higgins]

I think that the split between 'paid less than statutory employees' and 'paid less than are statutory employees' is a distraction here. In some sentences, including an extra verb is important to avoid ambiguity in the meaning. For example, the sentence 'Gillian spend longer on homework than Thomas.' has two different meanings. One is comparing the amount of time they spend on their homework (the sensible one), and the other is, well, I'll let you figure that out. To clarify this sentence, it would be better to write 'Gillian spend longer on homework than does Thomas.' This kind of ambiguity trap sometimes appears in GMAT problems.

However, the sentence above doesn't have that problem. The version with the extra verb (D) is fine, but the version without (B) isn't ambiguous so is also fine.