When Matt Arnold pulled his name from consideration from the Mets' GM opening, Jon Heyman said that Arnold signed an extension. This was in Oct of '21. And the Brewers have been quoted many times that they don't disclose the contracts of their executives to the public.
Then I found this from a CBS article
https://www.cbssports.com/mlb/news/brewers-president-david-stearns-steps-down-gm-matt-arnold-promoted/#:~:text=Arnold worked for the Tampa,Milwaukee for the foreseeable future.
My gut feels that it probably was longer than a 2 year extension, especially if they knew Stearns was probably going to walk when his contract ended.