You are correct, after reading the service contract again, I believe the transmission issue would be covered had I not inadvertently fixed it.
Earlier today, out of frustration, I decided to overfill the transmission. I put on my lift, let it run until the trans was at about 40 deg c, left it running, raised it up, removed the fill plug and trans fluid dribbled out. I figured that meant my fluid level was pretty close to where GM wants it, give or take a little.
From there, I let it drain while the engine was running until it was just a drip (which should be GM's desired level if I understand everything correctly) - then I added a full quart and went for a drive. The problem was lessened noticeably. And I could make the problem go away entirely if I tested the trans while going downhill. Fluid being pulled towards the rear and uncovering the pick up during acceleration seems to be my problem.
Back home, back on the lift, I put in another 1/2 quart. Off the lift, out the driveway, to the undisclosed test track by my house... The transmission performed as it should, no slipping, burbling, flares, etc... Just what a stock transmission should do. Shift gears, no drama.
I am sorry for everyone that I've engaged on this issue, and the time ya'll have wasted trying to help. In the end, another 1.5 qts of fluid took care of it.