Is there a technical way to understand clauses beginning with "whatever else"?

Hi all,

I'm struggling a bit to explain clauses that begin with "whatever else" or "whoever else."

For example:

We're inviting Alice, Bob, Charlie, and whomever else wants pizza.

My intuitive sense is that the sentence implies that Alice, Bob, and Charlie all want pizza. However, they are not technically the subjects of "wants."

Is this understanding correct; and if so, is there a technical reason for it? Or, are A, B, and C merely invitees without necessarily desiring pizza?

The same kind of question arises with

We see future problems in algebra, geometry, and whatever else is mathematically challenging.


Is is grammatically fair to say that algebra and geometry are consided mathematically challenging by the speaker?

Thanks,
Jeff