Yes they were. Your info doesn't give the seat color for 75' , and says that 76 had a brown seat, not that only the 76 had a brown seat. I have an original, unrestored, 75 super sport, brown. I ordered a seat cover for a 1975 f model around 1998 from a Honda dealer here, it is brown, didn't have the logo on it, go figure. Was browsing CMS a few years ago and they had an original seat cover for a 75 f model, ..brown.
Go look up the part numbers for the seat assembly and/or the seat cover for 75' and 76, ( either was available) same part number. Look up part numbers for the k's, they are different.
Look up the seat part number for a 77 f model, different....