I'm not against questions that are parent-related and increase traffic to our beta. The asker could have gone to BoardGames.SE or LifeHack.SE, but they felt this was a parenting issue. Even if they'd asked about cleaning a LEGO set, I don't think I would have sent them to Bricks.SE.
A SE or Google search will locate the question well enough. Currently, "how to flatten a warped puzzle" on Google brings up this question as the 5th result!
I think it's important that the asker chose to ask us. We are thinking about these questions from a parent's perspective. If we can offer insights as parents, or people who are cognizant of children's needs, then I think that is the dividing line.
For instance, on this question, I suggested a measure that included putting a sealant on the puzzle. As a parent, I felt the need to specify the use of a non-toxic sealant, or even a food-grade sealant, depending on the child. I can't say BG or LH wouldn't have suggested the same thing, but I personally only mentioned those options because I was thinking about it from a parent's point of view.
Questions about assembling a bed or a crib could potentially meet the same criteria. I've put together and taken apart my son's crib enough times now that I consider myself an expert. I would mention tricks I've picked up that have made it easier, and things I watch for to make sure the crib stays structurally safe between assemblies. Another site might just offer you help in understanding the building instructions, rather than providing you safety insights or tips.
So, my litmus test would be: Is the Parenting.SE community able to offer insights as parenting-minded individuals that other sites may not?
Although it wasn't brought up, I feel that this academia meta question/answer shows that migrating a question to another site can make access more difficult for new users, and it removes the community's ability to self govern. Letting us vote ourselves can be preferable to trying to catalog questions in just the right spot.
I would use my litmus in deciding whether or not to VTC.