I looked at the parts catalog for 2017 and it shows the Kohler. I guess they put as much effort into updating the website as they do supporting the stuff they sell.
I'm not convinced that emissions compliance was the sole reason for the change. John Deere is still selling Gators with the old Yanmar 3TNV70 and lawn tractors with the Minimax. I suppose Deere has a better relationship with Yanmar and Polaris got a better deal from Kohler.
I also just noticed Yanmar is selling UTVs now. It looks like a re-badged Yamaha. No diesel option.
The 3TNM72 904cc Minimax that was used in the Brutus has been replaced with a 3TNM74 993cc Minimax that is Tier 4 Final compliant. I'm not sure when it became available but as far as i know there was no gap in sales of the JD machines that use the Minimax.
Doing a little more research tonight, I found out the 3TNM74 was introduced in January 2012 and used by JD in their 2013 models. So the story about switching to Kohler for emissions reasons is not true.