I'm not sure that this is a useful difference. Physical ballot boxes often sit unattended overnight in the case of early voting centers (and in some cases even in regular voting locations depending on local procedure), and digital tabulators are usually observed at all times that they are unlocked. If anything digital tabulators may be somewhat more secure from this perspective, because they typically require authentication with a cryptographic token (which is held by the presiding judge of the polling location or a similar person) before they will count any ballots. This is a second measure preventing ballot stuffing when unattended as compared to a ballot box without on-site tabulator.

The issue is different for direct-recording electronic (DRE) or "paperless" machines, but this article pertains to digital tabulators that are actually a voting machine and ballot box in one: they scan the ballot and then retain it in a box for later audit. The seals pictured are actually used to secure the ballot box, not on the machine itself which sits on top of the box.