Constraints as a good thing? Yes and no…

I do agree that when solving a problem it is good to know the constraints on possible solutions, and as you say knowing those constraints can save time by narrowing the solution space.

But, I see constraints as part of the problem definition, and during your phase one — taking time to properly understand the problem — I most certainly want to challenge any constraints and understand why they are there. I want to make sure they are genuine constraints on the solution and not just the result of misunderstandings or bias. Once I know they are real, they become useful, but only then.