What the poster may mean is that a carbon steel pan must be heated slowly (i.e. on half power) until it is all the way hot. Then you can use a higher power setting if you want. If you don't do it this way supposedly the pan warps, but I haven't been brave enough to test whether or not that's really true.

That said, heating on medium until it's hot takes a few minutes at worst. I don't really see what the big deal is.