Quite late I know, but I'm just now getting around to 2020 taxes and I am similarly flummoxed by this QBI option. I also selected it and now want to de-select it to see what, if anything changes. I'm still struggling but saw Carl's request for the screenshot which appears (even if you DON'T make over $160k per year), and I found it again after randomly deleting some forms. Here you go:
