I've never heard of a discount for Adventures by Disney. There's nothing listed on the member website either.
But even if there is such a discount, understand that all discounts are subject to change at any moment. We've had many variations of discounts over the years on things like park tickets (AP discount is only about 3 years old), dining, recreation, etc.
I wouldn't suggest making discount programs a big part of your decision-making process. Any one of the perks could be eliminated next week or next year and members have zero recourse.