The tapes would have been baked to stop shedding due to their age. This has nothing to do with the performance of the tape when originally recorded
Actually, in the 70’s the tape formulation was changed to an “improved” formula. This new formulation simply could not withstand time and now require baking for new masterings.
Ironically, the tapes used in the 50’s and 60’s remain well preserved - assuming proper care has been implemented.
My remastering engineer friend has remastered albums from Nat King Cole, Sinatra, Peggy Lee, Beach Boys, Beatles solo albums, all the classic jazz albums from the 50’s & 60’s without needing to bake the tapes.