Fused relative phrase

Hi,

As time goes by, the cheerleaders become more choosy about whom they associate with and narrow their associations.

Should I look at the underlined part as an interrogative content clause or a fused relative phrase?

The meaning of the construction in question resembles that of the fused relative phrase, rather than that of the interrogative content clause.

As time goes by, the cheerleaders become more choosy about whom they associate with and narrow their associations.

=...the cheerleaders become choosy about the person(whoever that person is) whom they associate with...(fused relative interpretation)

=...the cheerleaders become more choosy about the answer to the question of "Whom do they associate with?"...(interrogative content clause interpretation)

But the fact that relative words 'who/whom' have a very limited use in the fused construction is bothering me: 'who/whom' are used only in a so-called "free choice construction".

ex) You can invite who/whom like.(You have the freeom to invite who you like)

Should I look at it as a variant of the "free choice constructions"?

Any suggestions are welcome. Thanks.