Sort of, apparently they don't get sufficient sunlight to grow, but (budget permitting) I'd have thought that it's within a head groundsman's remit to install hydroponics to rectify this problem. It seems like such an obvious answer that it's hard to believe that someone who gets paid to look after Wales' national stadium wouldn't have thought of it, so maybe there's a reason why it wouldn't work or hasn't been implemented.
As you say, it's not in Desso's interests for one of their pitches to be a lash up, so hopefully they offer sufficient after sales support to get past teething problems and make sure things work as they should.