More BS.
From:
http://navysite.de/cg/cg21.htm
GRIDLEY operated along the California coast until sailing for the Orient 18 November.She left Subic Bay 2 January 1967 for plane guard duty in the China Sea and the Gulf of Tonkin. After varied duties in the fighting zone, she sailed for Australia en route to the West Coast and arrived Long Beach 8 June to prepare for future action.
By my calculation, his first tour was five months and six days from Subic Bay to Long Beach. He did not "cut it short to volunteer for an even more dangerous assignment on a river combat boat." He went home with his boat.
As for "more dangerous assignment on a river combat boat", if you read the 7 part Boston Globe piece, you will find that when he volunteered for Swift Boat duty, those boats were used on the coast and the "river duty" didn't start until two weeks after he reported for duty.
Perhaps you should get your facts straight.