Not sure what that remark was in reference to, but ... yes, they can bring you negative apples.
Your enterprise can have an obligation to deliver apples to someone, which has all the same effects as negative apples and should be booked as such. If you acquired an enterprise with such an obligation, they gave you negative apples.
It's important to account for them that way in e.g. seeing the implications of the Put-Call Parity Theroem.
See, there's no such thing as negative apples. Sure, they exist in math - but they don't exist in reality. You can possess a chit that says you owe apples but, in reality, you only have said chit and do not actually possess negative apples.
The post may not have been clear enough, but the point was to show that it's still very much a philosophy.
Your enterprise can have an obligation to deliver apples to someone, which has all the same effects as negative apples and should be booked as such. If you acquired an enterprise with such an obligation, they gave you negative apples.
It's important to account for them that way in e.g. seeing the implications of the Put-Call Parity Theroem.