I think I was only hitting this during unit tests if 2 tests had the same view names, I changed my tests to avoid having the same view name in multiple tests to avoid this error, but unloading the app does not clear the tag registry.
In a normal case I don't think it should happen, but there is no way for me to check to see if a tag has already been registered, so I can not really prevent it.  Actually in the case of a duplicate tag being used, the template won't necessarily match the expected one, so maybe it is best to do a console.error() to alert the developer of the problem?