To be clear, what we have now implemented in master for the upcoming release is no change in BookBrowser at all (i.e. tooltips will tell you if any specific semantics are set, as will Reports, as will content.opf guide, as will the nav landmarks). We have chosen ... after a bit of pushing
... to add a checkmark after the currently selected semantic in the Add Semantics dialog.
That has been pushed to master and appears to work just fine.