Yes, they posted transcripts. The transcript said "Tplush stop making silly comments, of course they didn't post the transcripts".
I'm going to believe that Corbin Burnes didn't pull that comment out of thin air, feel free to continue to believe that he did if you'd like. Maybe he paraphrased, but I also struggle with how the Brewers could have framed in a non-negative/trashy manner that Burnes performance helped cost the Brewers a postseason run. There's not really a good way to say that, especially to the guy that was the literal best player on the team last year. You also have a handful of notable former Brewers that have similar hard feelings, Hader came out of a hearing and all of a sudden was adamantly a 1 inning pitcher. Coincidence? Or maybe the fireman role doesn't get as much in arbitration so he was adamant about being a 1 inning closer only.
I suspect Burnes does have a pretty decent understanding of the process as he came up with a pretty good/reasonable comp in Bieber for what his increase should be. He probably was thinking "there's no way my increase should be less than this guy" considering he's been the clear better pitcher the last 2 combined years. I suspect him thinking the offers were poor reflect that.
As much as his comments weren't a very good strategy play for him going forward, as a fan I applaud him for calling out bad behavior. Otherwise the Brewers can more or less get away with it and avoid the public scrutiny they deserve.