My 2017 8289ws came with a Reese Revolution . Research tells me the Sidewinder hitch is about the same hitch, other than some differences in the way it mounts.
My dealer led me to believe that this will become standard on Rockwood products, although I can't find anything online to support this.
I have only pulled it once and have yet to get used to the whole 5th wheel thing. Looking forward to useing it again next month!
Some details about the Revolution: