I can confirm this. A Brother HL-L3270CDW color laser worked fine with third-party toner at first, but would not recognize it after a firmware upgrade. I tried three different sets of cartridges, including different brands - none were recognized, and there's no way to revert to a previous firmware version.
That was the last Brother color printer I'll buy, unless they go back to accepting generic toner.
That was the last Brother color printer I'll buy, unless they go back to accepting generic toner.