Again, that's not a business relationship, that is quite literally exactly how feudalism worked. Your liege lord was not an expert on your plot of lands agronomy prospects or the physical state of your knights, so he had to trust you.
Its possible some of the confusion is state based vs action based. If you define business relationship by state, then absolutely anything that happens in a cube farm while wearing a tie is a business relationship, from a free market to blackmail to slavery to blind faith. If you define business relationship by action as a theoretical ideal of how roughly equal participants in a competitive market in a rule of law system treat each other, you get a completely different analysis.
Its possible some of the confusion is state based vs action based. If you define business relationship by state, then absolutely anything that happens in a cube farm while wearing a tie is a business relationship, from a free market to blackmail to slavery to blind faith. If you define business relationship by action as a theoretical ideal of how roughly equal participants in a competitive market in a rule of law system treat each other, you get a completely different analysis.