The bigger concern with Paypal is chargebacks. For digital goods (like GRC) the payment can be reversed for SIX MONTHS from the day it was made, no questions asked. There are far too many risks associated with this.

Even if people are legit now, what is to stop someone from making a chargeback down the line if their wallet breaks? Or the GRC value plummets? Or if they are suddenly 'strapped for cash'?

Too risky. No-one will, nor should, sell crypto with Paypal.