I think people should keep by default the access that the person had gained on their own merits if their employment circumstances change. Specially given that it may include functions that were appointed by their community, with the wiki drama it may ensue (not to mention if that temporary removal of rights also affects two more users).
However, you make a very good point that actions taken should not indirectly leak if they left in good standing with the WMF or not.
How about leaving the rights not given due to his job by default, but mentioning that in their exit interview, the employee will be asked if, in addition to that, they are interested in keeping any extra access he may have as he is interested in contributing in the future, or even if they prefer that earlier ones are also revoked.
This way, mentioning in their offboarding that all rights are to be revoked does not leak whether that's being forced on them or simply because they are fed up with wikis and stated in the interview that they prefer to have everything removed (at least temporarily). It also makes things more efficient by leaving the final rights in one step.