I think the difference they are getting at is something akin to this.
In one situation you run a stall and buy products from people to sell at that stall. At some point you use what you've learned doing this to sell your own product.
In the other, you don't buy anything from anybody. Instead, you rent out a stall for other people to sell things from. You then watch the stall and use that information to open your own stall.
The first case seems pretty normal to most people, I think. The person you were buying from originally doesn't inherently get some kind of assurance that you will always buy from them in the future. There's no difference to the seller if you buy from somebody else, don't sell any of that product, or make your own. We just don't expect that buying goods from somebody inherently adds any other kind of obligation. It's two equal parties making an exchange, and nothing more.
The second case, however, I think is not so clear cut. All of the sudden you have a lasting relationship between two unequal parties. These are the sorts of situations where you tend to find more implicit or inherent obligations on the participants. It's no longer the guy you sold that thing to not buying from you again, it's your landlord competing with you.
I'm not trying to pick a side here, so much as I am trying to explain why people might not see the two situations as identical. And of course there are plenty of real-world complications too.
In one situation you run a stall and buy products from people to sell at that stall. At some point you use what you've learned doing this to sell your own product.
In the other, you don't buy anything from anybody. Instead, you rent out a stall for other people to sell things from. You then watch the stall and use that information to open your own stall.
The first case seems pretty normal to most people, I think. The person you were buying from originally doesn't inherently get some kind of assurance that you will always buy from them in the future. There's no difference to the seller if you buy from somebody else, don't sell any of that product, or make your own. We just don't expect that buying goods from somebody inherently adds any other kind of obligation. It's two equal parties making an exchange, and nothing more.
The second case, however, I think is not so clear cut. All of the sudden you have a lasting relationship between two unequal parties. These are the sorts of situations where you tend to find more implicit or inherent obligations on the participants. It's no longer the guy you sold that thing to not buying from you again, it's your landlord competing with you.
I'm not trying to pick a side here, so much as I am trying to explain why people might not see the two situations as identical. And of course there are plenty of real-world complications too.