Do you have an ethical problem with this?
Book a 1 night campground stay and use it.
Go stay with your parents for the next 6 nights.
Is it OK if the person who stayed at the campground books ADR's for all 7 nights?
Personally, I don't think it is - but whatever, if you think it's cool then good for you.
Is it OK they get $50 worth of magic bands because its cheaper to book a throwaway room than buy them separately at $13/each?
They are NOT getting a week's worth of benefits for one night. Not sure where you are getting that from.
They get a magicband, and two days of parking and EMH access. They can book an extra day if ADRs at the 180 day window and an extra worth of FP+ at the 60 day window. The major difference is that they can continue to book FP+ 60 days out from any given day after the reservation until their check-in date.
How is that not a weeks worth of benefits (minus parking, which they would pay anyway)? In the FP+ thread people will sacrifice their own parents for an A&E FP+. The ability to book ADRs & FP+ is a huge benefit.
They are getting 2 days worth of parking, and a magic band for each member of their party - any more than 3 people and you come out ahead, and the FP+ and ADR perks. And the benefit of staying off-site (whether you want to view that as a cost saving, or more amenities for the price, either way).
So if you take 3 parties, with the exact same details (size, dates, touring plans, desired ADRs, etc) but one stays on site, one does throwaway room, and one stays completely off-property, who comes out ahead?