I think we decided at some point that both the train on your itinerary and the train you wish to get must be unreservable.
Not sure who 'we' is or what qualifications those people possess, however your conclusion above is certainly not one of the alternatives that Q25 implies.
Q25 - Can a passenger with an Advance ticket travel on an earlier connecting train?
A: Yes if it is non-reservable, no if it is reservable.
If 'it' refers to the advance ticket and the suggested or booked service, then they can travel on an earlier train if the suggested service is non-reservable. No requirement for the earlier train to be reservable.
If 'it' refers to the earlier train, then if the proposed earlier train is non-reservable then the customer can travel on it (regardless of whether the booked/suggested connecting train is reservable or not).
This is of course only my opinion, based on this Q25 in isolation (which doesn't form part of the customers contract) in any case, I don't think.