I am going to say, Yes! Offset hose started out in the beginning of 1969.
Only have Dearborn cars with the early box and the offset A/C hose at the firewall. My sample size ranges from the beginning of production, until at least, late January. That is 4 cars that have the lines or remnants remaining. All of my 1970 cars have the straight A/C hose.
No straight hoses on early boxes found, nor offset hoses found on late 1969-70 boxes. My samples of 1969 Cougars with remaining hoses are all the early variety and Dearborn. My 1969 San Jose Cougars ceased production about the 4th week November 1968. Zero San Jose samples found intact.
As time permits, I will try and look for ink stamps to narrow the changeover. Not any good boxes remain for sale though.