Turns out this isn't a bug. In PassThru pot mode, the pot becomes active only *after* the saved parameter value is "passed through". In other words, you can't actually navigate to the saved parameter value until the pot has become active, and when the pot becomes active it is either one value above or one value below the saved parameter value. This is to create continuity between the saved parameter value and the pot pickup. So, this feature is working properly.