That's solid advice for someone new to timeshares but as long as you use a contract and a reputable closing company that keeps the funds in escrow until the deed is recorded (and can also help with the contract) then there really should be no risk and the seller can save the 8%-10% commission.
We started with Westin/Marriott timeshares and bought mostly resale without brokers. Since
DVC transactions tend to happen primarily via brokers, we bought DVC via brokers. But if I were to sell one of our DVC contracts, I'd definitely first try on my own. I wouldn't do it on Facebook - the level of scamming (and fear of scamming) on those groups is too much. Unlike a home, that requires inspections and the one nextdoor may be completely different, selling a timeshare contract/deed is a relatively simple process.