I've seen a lot of the "old stuff" that is dry and cracked. Until a few years ago, almost all the "putty tape" was the clay type. Butyl tape has only been available for the past 5 or 6 years (at RV stores). The manufacturers, being concerned with cost, still use the clay putty tape ($1.50 a roll) where they can as opposed to using Butyl tape ($6.50 a roll). They have been using more and more butyl as the years progress, but on things that don't move and don't get a lot of stress, they still tend to go with the clay stuff.
Unfortunately, it seems to last "past the warranty" so the manufacturers are "satisfied".... Us, however.......