That's what I'd guess. I finally experienced what the OP was talking about last night. I normally use a lap desk and that evens everything out and makes putting your palms down more comfortable. I didn't have my lap desk last night and eventually my palms got sore from the sharp corners.
This happened as well with my Intel MBP, but to a far lesser degree.
I have very fleshy hands so it takes a lot for something to press into my hands enough to cause discomfort. It wasn't bad to me, but for someone with thinner hands I could see it being quite unpleasant.
Lap desk. Get a good lap desk with a built in wrist pad... or just get a wrist pad for table top use.
Well I also wondered a few other things too. Like if it was a production variance from the milling of the aluminum top case. Or if the space grey models would be different because they are anodized. Or over time, normal usage smoothes out those rough edges, much like the weathering of rocks from water.