If Orbitz can't get a discounted room, they quote rack rate, just like Disney. And that's what I see on Orbitz - the Garden room doesn't have the "up to 25% off" text next to it, like some other room categories do, and it's showing as $241. Why it's $1 higher than Disney is not clear; they seem to be adding roughly $1 to the rack rate for no good reason. If you try to book via Disney, you see that the Garden view rooms are not available at the discounted rate, but are available at full price.
When I checked Aug 10-12, which is also in Summer season, the Garden view rooms are available at the discount rates on Disney. I get $240/night for regular rates on Disney or $180/night with the discount, and $181/night on Orbitz, which is roughly 25% off as expected plus the extra $1. If I add the REVIEW15 code that MouseSavers lists, then the rate goes down to $157/night, which is just under 15% off (Orbitz doesn't take the 15% off the tax, and of course they add their $1).
So I'm not seeing any huge discrepancy, other than Orbitz adding a mysterious extra $1/night, but that's pretty common for OTAs. Charge an extra $1/night and over time it adds up to extra money. Most people don't quibble over minor differences in price. It's the "extra profit" fee.
Disney shows room rates without tax, but MouseSavers shows rates with tax. That's almost certainly the discrepancy. When I check some Summer rates, MouseSavers is correct once you add tax.