The reason is that the combination of Sensi-Temp (a TOL feature) and no P*7 is unusual. You later found Sensi-Temp only on upper-end models equipped with P*7.
But this is the time frame just before P*7 was introduced (Fall of '63), so the Sensi-Temp is not out of place.
I probably shouldn't have said "TOL." "Upper-end" is more descriptive of the ranges GE put Sensi-Temp on.
An example would be my J 370 30-incher from 1972. That model was one model below the TOL J 757, but it still has Sensi-Temp (and P*7). The J 757 and J 370 were the only 30-inch free-standing models that had Sensi-Temp on them that year.
In fact, my J 370 was available in a non-P*7 model, the J 330. If you opted for the J 330, you didn't just lose P*7 - you didn't get Sensi-Temp either.
So, "upper-end" is probably a better term than "TOL," because the feature was applied to upper-MOL units as well as TOL ones.