There's a reference to the funeral, so it's being implied that Hoffa raised the flag before the funeral.
Maybe he had the flag raised back up late on the 25th, after the funeral. Or the following day. Maybe it was a decision out of Hoffa's hands.
According to an account from an official who was at the Teamsters Headquarters in DC, Hoffa in Miami on the 22nd complained that the flag had been lowered at the Headquarters. Could be that over time this evolved into Hoffa personally having something to do with it being raised back up. Some accounts have Hoffa ordering the flag not to be lowered and that it wasn't.
Took at the dramatic license the "JFK" movie took and how truth was distorted.