Note the definition of "debt" is not defaulted loans, it is loans in general.
A case could be made that banks' principal purpose is collecting debt, since the obtained-prior-to-default exemption in (F)(iii) (which serves to modify the debt definition into what we currently think of it as) only applies to third party debt collectors. Using this proper definition of "debt," the "principal purpose" segment of the debt collector definition could have been considered.
I'm sure this isn't the intend of the legislature, but it is, in fact, how the statute reads. This reading would have serious consequences for regulation on a state and federal level, and likely would never be endorsed in an opinion.
I see that I'm about a month late to the discussion. It was a good read.