The seven days is a new one to me.
US sellers, based in the US not just listing on dotCOM, get their Held payments after the buyer posts positive feedback or 21 days whichever comes first.
This allows ample time for arrival if the buyer doesn't leave FB.
The Rest of the World get the Held payments after 21 days, no earlier.
You know that you are supposed to ship within 7 days, or lose your Seller Protection, right? That may be where the 7 days comes from.
And you know that Paypal will release the Held funds earlier to pay for PP shipping labels? And that you can get from 5% to 17% off PO counter prices on PP labels?