This is the expected behaviour. As the Help says (Import Wizard - data format) “When a location is matched to a location in your location hierarchy, its name from the location hierarchy will be stored in (Survey) Event Location and Sample Location and the imported data will be stored in Event Location Name and Sample Location Name, if there is no Location Name for the observation in the import file. If Location and Location Name are present for an observation and Location remains unmatched the two will be concatenated and stored in Event Location Name and Sample Location Name. If Location is present and Location Name is not present, and Location remains unmatched the Location will be stored in Event Location Name and Sample Location Name.”

Note that if the two are concatenated and they exceed the Location Name field size (100 characters) the result will be truncated.