For the record, such holds are not regulated by Regulation CC.
It is however governed by the card associations. From the Visa Operating rules on Visa Checkcard transactions, pre-auth holds must be released:
"When a matching Clearing record is received, but no later than 3 business days from the Authorization request". There are additional rules in effect for real-time auths.
My guess twana is a PBF bank like us. We do not receive the hold records on pre-auths in our settlement files from our processor, so they're not placed against the account balance on our operating platform. However, at least they reside on the card balances. Another argument for real-time!