Old Forester uses different profiles for its 'Signature' 100 proof and standard 86 proof expressions. The 86 isn't just the 100 with more water. I suspect this is also true of the Wellers, though that is by no means assured. The easiest way to make a product at multiple proofs is to start with the highest, bottle that, add a little more water, bottle the next one, and so on.
Another factor, not applicable in either of these cases but applicable to Very Old Barton, for example, is that if the 100 proof is a bond, then it must be all from one season, whereas with every other proof point they can mix in older whiskey and even whiskey from other distilleries.