Which I said as well.
Even with every hotel room filled, the offsite industry would still be bustling b/c Disney doesn't have enough capacity for every guest that goes through the gates. I disagree that the perks (or perceived lack thereof) are the only (or even main) reason why people are staying offsite.
Disney resorts are expensive. Even the values are expensive for what you get. We paid less/night to stay at Shades of Green and got a larger room (seriously it feels like double the size of an all star room). That alone (completely forgetting the EMH perk that SoG guests do get) is enough for me to stay there as opposed to a value resort. My brother/SIL/nephews stayed at All Star Sports (there isn't a good acronym for that

) in March, and I felt like a sardine in their room. I would not have stayed there having to have a pack n play for DD in the room, it was just so tightly packed. I've been in $60/night rooms that are bigger than those rooms are.
See, and for me we do stay offsite, but it's not because of the lack of perks. It's pretty much because of price. Now, if SoG didn't have the location it did, I might change my mind - but again, that's strictly location not any other perks. I just don't know that I'd want to go out to International Drive every night...I like being close to the parks. So if we couldn't stay at Shades, we'd likely stay at a moderate resort rather than go further away. I mean, I'd love to stay at the GF or Poly instead, but I can't justify the cost...it's 3-4x more expensive to stay there (depending on time of year) than Shades of Green. They're beautiful hotels, and we have stayed deluxe before, but we can't afford to do that every year.
I still contend than a 10 day advantage would be quite a sizeable advantage when this is all rolled out, just as it is for ADRs.