No idea why the axle gets replaced too. Listed on the receipt as a CV joint/axle. I peered underneath, looks like a new left axle. Shop was able to get CarMax to pay for that part of the repair, so I'm all good.
Guessing it's possible an improper shape/profile of the axle at the sealing point could be the issue that causes the failure? In which case replacing just the seal would not be a sufficient long-term repair.
The full synthetic fluid is very nice. Down in the 30s here this morning, shifting was still silky smooth. Will be interesting to see how well it works in Jan/Feb here, which can get down to -20.