We do not currently track all changes related to UI Extensions as they map to versions of POS.
When we originally designed the data model for POS UI extensions, we made an assumption that an explicit undefined would traverse the transport layer between extensions and the host, but it does not. So typically where you see optional props that show a UI element, try null to hide it. In this particular case, the component in POS that the badgeValue maps to was not expecting null. I changed the POS to expect null and to treat it like undefined for this case.