I can see a common thread of building in all the areas listed.

Vintage - restoration.
Homebuilts - building.
Warbirds - restoration.
Aerobatics - restoration/building.
Ultralight - building/restoration.

And I equate restoration with building; replacing a rib, recovering, welding, etc. seems like it would more than a pain in the rear end than scratch building.

To become a member of the Modern Aircraft Club only requires a checkbook. Hey, we get it - somebody bought a new C172. Good for them - really, good for them - but I don't know why they should get a ribbon for it.