I guess my thinking is that the reason the V.A. considers an illness to be service related is that the root cause of the illness is/was believed to be due to something encountered during military service. I'm very glad that ALS now has an automatic service related assumption. In my mind, this means the V.A. assumes the cause of the illness was due or at least could be due to something encountered while in the military that acted as the trigger. So, they take responsibility.
While it is recognized that PLS has longer longevity attached to it, it is also recognized that the diagnosis often changes to ALS if LMN involvement ensues.
What one could logically conclude is that the V.A. takes responsibility for motor neuron disease only if it involves both upper and lower motor neurons but not if it only involves upper or lower alone. If life expectancy is the answer, so be it but that does not explain "assumption" for service connection (well, at least not in my mind).
If the V.A. is going to assume that military service is responsible for one motor neuron disease, why not assume it is for every motor neuron disease? This is my question.
I need to ask this directly to the V.A.