OK, let's try the math. For example, JFK-CDG prices at $3800 one-way in full-fare business. I believe, other than corporate discounts, this is the only fare that would book into J class. If you're doing, say, an AONE5 at $10,000, the revenue AA gets for that segment is likely significantly less than $3,800. Hence, it books in discounted D class.

If you're looking for a "consolation" prize of not having to deal with capacity restrictions, sorry!