For all licenses that have this restriction, the limitation is contractual, not technical. Salesforce doesn't monitor whether or not you go over this limit. I doubt that contractually they would enforce this for an object that the users aren't directly accessing.
See sfdcfox's answer about this:
There are no technical restraints regarding the ten object limit. This is actually mentioned in the documentation somewhere. However, if salesforce.com finds out (however that may be), you would be in violation of your contract and at risk for contractual breach.
In theory, this means you'd be forced to pay for the more expensive
licenses that you would have paid for if you'd been upfront about
needing more than 10 custom objects to begin with, backdated to the
point where the breach of contract occurred.
As long as the users can only view data from ten different custom
objects, they should be fine under the contract. For example, it would
be particularly cumbersome if you couldn't write a trigger to update
an 11th object they don't have access to when the trigger does so for
users not under the 10 object limit.