This is just my opinion, and only that, but I think that's terrible. If they season the cast, I don't see how it could be out that far.
I don't know what Steel City uses as a flatness spec, but I recall reading something a while ago that said that they season tops for 6 or 8 months before they finish them off. Maybe I have them confused with someone else - who knows.
But one thing is for sure - you can't use any 0.015" tablesaw top to lap handplane soles.
My delta hybrid is just north of 0.008" hollow from front to back, and I wasn't pleased with that.
It's just a sign of the times, I guess - do it quickly and cheaply.