New spell check highlight--how to disable

Because somebody mentioned that the objectionable feature relates to tablet use, I am reminded how in Windows there is an option to enable or disable tablet mode on devices with touch screens, including some laptops. Since you are on a Mac, I right away wonder whether your Mac is of the 2018-2019 model era at least, and if so, if it has one of those touch-sensitive strips below the screen and just above the keyboard, by the hinge. If so, it might be that Word is being triggered by this to be in tablet-support mode. I am working on a Mac at the moment but lack sufficient familiarity with the platform to be authoritative, but I notice that when I search on "touch" in the MacOS settings app, one of the things listed as a setting related to Touch Bar is "Touch Bar typing suggestions," which it identifies as being in the keyboard settings. You can specify there not to check spelling as you type--at the OS level--with Word still doing it for itself, and still displaying the red squiggly line. My version of Word is not current enough on the Mac to display the red highlight you describe, but since it is touch related (so the thread thinks) I speculate that disabling the keyboard setting for checking text as you type, might have some effect on this, if Word is paying attention to the touch status of the OS settings. I know this is a long shot, and I apologize I lack the specific setup to test the idea out all the way, but I thought it just might pertain. Best of luck.