Hi Steve,
I think I see your point. However, if Competitor A buys low quality links to Competitor B, yes, they can use the disavow tool to remove the links and it will still take time for them to do so and effort but what is the point in this. Why is competitor A spending their time and money trying to harm Competitor B when they can simply protect themself with the Disavow Tool Why not spend those time and money on building quality links.
Competitor A is simply wasting time and money to buy links where Competitor B is spending time and effot to remove them. I don't see why anyone would do that.