Certainty no longer for use on cool season grasses

The Purdue Turf Tips blog had a post this week on Certainty herbicide. Monsanto, the company that makes it, recently changed the label removing uses on cool season grasses. This went into effect in May.

I purchased my bottle in April so it is the "old" version, but I noticed on my last application that the online label had changed. I had printed it out, but couldn't find the directions for Kentucky bluegrass or any cool season grass - the entire section was gone. So, I had to use the instructions that came with the box instead. I thought it strange.

Now, apparently, it's official. The questions and answers on the Purdue blog didn't answer my biggest question: why? And I wonder if it can still "unofficially" be used on cool season grasses? I did a little searching on their website, but couldn't find any additional information.

Since that is no longer an option, I guess that leaves Chlorsulfuron-based products such as Nufarm Corsair (previously owned by Riverdale?) as alternatives.