So far I'm 5 for 5 when asked for a 50/50 partnership (where I do all the dev work and my partner is the 'idea man') and then never hearing again about the idea after I asked they put together this document - all without having to say 'no'. There has not been bitterness on their part, because next steps are on them.
In the off-chance they will actually do this (and it hasn't happened yet), I will take it seriously and really consider it. But even if I decide not to pursue it, I feel like the exercise isn't a waste of their time as they will be able to use it when looking for funding or other partners.
On first blush, it seems to set an adversarial tone rather than a collaborative one. On the other hand, it's good due diligence and probably filters out the serious from the not so serious.
I mostly agree with your response. I think the only place where it may not work is when the person wants a thought partner to help think through these things. There isn't always a strict dichotomy of duties in the framing of a venture - I think all partners should be involved in that. Different story when it comes to execution, though.