Not true. I sold a condo to Opendoor recently and it was unlisted, just a private transaction. They overpaid very generously too.
How do you know without getting bids from the open market ?
You can see the transaction history here:
https://www.zillow.com/homedetails/125-Mays-Blf-Fayetteville...
Add in whatever fees go along with the sale, and they're out a fair bit more than that.
Opendoor still holds it, Zillow is already marking down a similar one by 14%.