Yes, of course it can be divided, and I've never heard or read that it doesn't "like" to be transplanted or divided. I can't think of any logical reason for someone to print or say this, unless they personally just made some bad divisions/transplants.

Both 'Karl Foerster' and 'Overdam' are selections of a grass hybrid (Calamagrostis epigejos x arundinacea) that rarely produces viable seed. Therefore the vast numbers of these selections that are available in the market have almost certainly been propagated by division.

Hope that helps.