It seems extremely relevant to the market definition that the alleged alternatives aren't actually substitutes for one another.
If you have a car that runs on diesel fuel and there is only one company that sells diesel fuel, it seems like you want to claim that it's irrelevant and isn't a monopoly because there is another company of the same size that sells gasoline. Is it not relevant that you can't actually use that in your car?
It seems extremely relevant to the market definition that the alleged alternatives aren't actually substitutes for one another.
If you have a car that runs on diesel fuel and there is only one company that sells diesel fuel, it seems like you want to claim that it's irrelevant and isn't a monopoly because there is another company of the same size that sells gasoline. Is it not relevant that you can't actually use that in your car?