The article stated due to the life of the batteries, you can use old ones for up to a year after you received them. Sounds like it won't let you opt out if you don't have any live bands attached to your account in that time frame.
Edit: "The new update gives those guests who are staying at a Walt Disney World Resort hotel the option to opt-out of receiving a band, with the proviso that they have an existing MagicBand already active on the My Disney Experience account, and that the existing MagicBand is less than 1 year old. MagicBands have a non-replaceable battery, so the operational lifespan is limited."