Do I need to use IAP if I'm allowing users to sell virtual goods to each other?

My team is building an app where we will allow some users to sell virtual goods (videos, PDFs, etc) via our platform, to other users. We would take a cut as the facilitating platform. I can't quite figure out if we need to use IAP for our app - it doesn't make much sense if we're allowing users to sell their own goods.

I've been researching other apps and found that Patreon doesn't use IAP. I understand that their model is technically a donation, but Apple guidelines specifically mention that gifts/donations should be 1) not associated with any content and 2) all the money has to go to the person who was gifted. Neither of those are true for Patreon. I wonder if its simply because they have a website as well?

Wondering if anyone has any experience with this as I can't seem to figure it out.
Do I need to use IAP if I'm allowing users to sell virtual goods to each other?
 
 
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