Thanks **bleep**,
From your video example and explanation, I believe I understand.
In the video, the user 're-orders' the blend before the sketch. Not sure why this is done, I would not teach my students this type of behavior, for exactly the reasons you mention (it would break parent-child). I see that by adding the project curve, you are trying to make it more 'robust' for potential re-ordering. But I still abide by chronoligical modeling, so I try to teach those guidelines.
I did try to duplicate your steps in the video, but after I re-associate the projected curve to the rear edge, finish sketch, I was still getting the Warning Information window: Parent of the point is either misisng or modeled away..then I realized, in your video, your CSYS was placed at the bottom left corner, while mine defaulted to the upper right (the one that was removed with the blend re-order)...so alas, re-ordering like you have done may come with more baggage than I'm afraid the project curve enhancement can alleviate, so I remain extremely cautious upon most feature re-orders and continue to teach my students the same.
Thank you though, I love to see and hear about other workflows.