Based on reports here and on other boards, it appears that if your trip was booked prior to the announcement that complementary bands were going away for 2021, you are grandfathered in at $0 for the plain bands.
I have a trip in May 2021, and those bands show $0 as well. My October trip (made after the announcement) show as $5.
It is highly unlikely (like 0%, imo) that Disney would ever come back and try to charge you at a later date, once the bands are ordered.
Steve