In the help document there is a hidden preference where you can disable the sync of tags between index file/folder in MacOS and item/group in DT3. I have tested it myself.
But it takes sometime for cleaning up the tags in MacOS folder if you want to not showing the tags in MacOS after setting the preference. I’d suggest you test it with a sample or wait for final version to enable the preference.
et al:
Bear in mind this hidden preference disables both importing and exporting Finder Tags and also inhibits exporting Tag data for use with Spotlight.
Keep in mind that this will not remove Finder tags already assigned to files before you imported them into DT and before you disabled the Finder tag integration in the hidden preferences. Those will remain with the files unless you manually remove them via Finder.