I think there needs to be a digital component but it can still apply to physical goods. Either way, “warranty void if removed” stickers aren’t a control. It only applies to “effective” controls:
For the DMCA, circumvention means that there is a user attempting to “descramble a scrambled work, to decrypt an encrypted work, or otherwise to avoid, bypass, remove, deactivate, or impair a technological measure, without the authority of the copyright owner” – assuming that there is a technological measure in place that “effectively controls access to a work.”
If you need to reverse engineer the product to bypass the access control, then that generally qualifies as an effective control. But if you can just press F12 or Escape or remove a sticker, that wouldn’t qualify as effective.
(For what it’s worth I am not a lawyer and this is not legal advice.)