Well I disagree with that to some extent. There are definitely genetics that favor less dry down.  Probably not faster dry down, but there is a difference in dry down. I've knowingly planted numbers with a lesser drydown factor.   We chop most of ours so I don't care as much about dry down genetics, but if we do try to bale, it's like drydown runs into a wall  getting below 30 percent moisture.  Have seen it for quite a few years here. Have a twinmax machine and do custom, so have a good sampling of other options.