Ah, yes, I missed that in your code. Obviously, you can insert single column just once...
Anyway, U++ still has a way around. ArrayCtrl (and therefore SqlArray) columns and widgets are quite loosely coupled with "indicies" in row. Specifically, you can use two "entities" to point to single row "index".
Practically, you should use AddCtrlAt in your code where you want just single column with two "visuals":