Not according to reporter Thomas Lipscomb who has done some heavy investigating on this.
It doesn't take any heavy investigating. The Gridley's operations are listed on Kerry's fitness reports. (I don't think there's any dispute about his November 1968 - April 1969 Swift boat time.)
Tet Counteroffensive (30 Jan - 1 Apr 68)
Kerry arrived in-theater on Gridley at some point during March 1968.
Vietnamese Counteroffensive Phase IV (2 Apr - 30 Jun 1968)
Gridley departed the operating area on 5 May 68 for transit home via New Zealand.
Vietnamese Counteroffensive Phase VI (2 Nov 68 - 22 Feb 69)
Kerry reported for Swift duty in November 1968.
Tet 69/Counteroffensive (23 Feb - 8 Jun 69)
Kerry left Swift duty in April 1969.