I see "disruption" as either removing middlemen (disrupting supply chain) or changing consumer expectations in a market. Adding a middleman in the supply chain isn't disruption so much as making it more efficient for producers to reach consumers.
If you go by the Clayton Christensen definition, a disruptive company is basically one that starts off selling a product that is inferior to the accepted standard along most dimensions, but not all (usually it is much cheaper). Eventually the dimensions that were previously considered important erode or become altogether irrelevant, and suddenly the company focused on the lower-end segment finds itself in a position of dominance, while the former heavyweights are playing catchup.
I agree that it is an often overused term and one which is too often used to describe innovative business models or small startups. I don't see how it applies here. That said, a business certainly does not need to be disruptive to be successful. Disruptive companies are extremely rare and only come along once in a while.
I once had a professor who said that a great way to spot the potential for a disruptive product is to look for situations where you find yourself using a hybrid model- that is you use two or more solutions to solve a single problem. One meets a single need but not enough to replace the others.
I don't see any reason why a middleman that's doing something innovative shouldn't be considered a disruption.