You are missing the point - whether their motivation is purely profit, or altruistic, or whatever - if they do not want to fund a project, they have an incentive not to vote 'No' against it because as soon as they do they can no longer remove their money from the DAO, and have committed to funding the project if it passes.
The author conflates an (presumably autonomous) individual's true preference with necessarily increasing the net worth of the DAO. There is no a priori reason to believe that.
Edit: you could, like, you know, post a reason to believe the equivalency.
I think .. I believe the point of the featured article was the example:
(given the voter is mainly interested in profit, then) IF a voter thinks that the proposal will yield profits and increase the net worth of DAO: vote yes
but only if their interests align that way. if they don't, obviously their decision will be based on other factors.
the point being, it should be straightforward and obvious to vote yes or no, depending on whether the result of a majority-vote yes or no, would align with your particular interests yes or no.
while that statement seems almost tautological, it's a very desirable requirement for voting systems. I'm not 100% sure on the terminology (it's been a while since I studied it) but it might be called "monotonicity" or something.
the point of the article was that in some cases it would be advantageous to do something different instead of voting yes or no along with your particular interests. in this case that it would be better to split than to vote no, in many cases. that demonstrates the (mathematical/logical) assumption of monotonicity (if it was called that) is violated.
but you only need one example to demonstrate that. so it doesn't quite matter that this is not everybody's incentive, as long as it's a reasonable incentive that people may choose.
I admit the added bit about "increasing the net worth of DAO" raised my eyebrows as well. I just assumed many profit-interests would align with the net worth of DAO, and that it'd be healthy for the system or something (I don't know).