I'm not certain but I believe that the 722.6 holds 8 Liters. Since I pulled the transmission pan plug and the torque converter plug, I suspect that the only fluid that didn't get drained is the fluid in the lines to the transmission cooler.
At $10.50/Liter the "disconnecting the line" technique can get expensive. Also with the "disconnecting the line" technique the trans filter doesn't get changed or the bottom of the trans pan doesn't get cleaned.
I agree that with the "disconnecting the line" technique you change out more of the old fluid but either technique is better than not changing the fluid at all.
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles