Why is "them" and not "those" correct?

I have been preparing for the SAT, and this question has been confusing me a lot lately.

Some scissors (A) are designed for left-handed use, although most (B) of them (C) sold in stores (D) are not specialized.

When I initially read this sentence, I thought that B was incorrect (of them). I thought that it should have been "of those."

To my surprise, however, there is no error in this sentence.

Why is "of them" correct and when would it be appropriate to use "of those"?

Solution 1:

I agree with you: it should be those, because the participial phrase that follows it (sold in stores) is of the defining type, and defining phrases are normally not combined with personal pronouns. They can be combined with personal pronouns, but I suspect unusual circumstances are required for that; at least in this case it sounds off to me.

Solution 2:

Using "those" would actually convey the meaning, those scissors designed for left-handed use.

Some scissors are designed for left-handed use, although most of those [=those scissors designed for left-handed use] sold in stores are not specialized.

Sounds like a load of nonsense, uh?

And so, one way to make the sentence logical is to substitute "them" for "those."

Some scissors are designed for left-handed use, although most of them [=most of the scissors] sold in stores are not specialized.