Of course, the partner being asked to sign such an agreement can reply with a prenup of their own dictating how the partner in business will define compensation and dictating what will be considered as individual compensation from the business along with committing to making all such individual compensation joint income to the marriage, and so on.
The thing is, if it's a financial joint venture instead of a marriage a prenup is way too little, not way too much.
Other than that, I don't see it.
Quite agree.