When exporting Experience Fragments from AEM 6.5 to Adobe Target, they appear as 'HTML Offer' type, instead of as an 'Experience Fragment' type that all tutorials show. There is a valid IMS integration between AEM and Target. Does this have anything to do with Link Externalizer in AEM?
What version on AEM are you on? There is a known issue on AEM on v6.5.5 and lower. A workaround is to use the Target legacy API for integration. Note: Once you upgrade AEM to v6.5.5 the legacy API is completely deprecated, so, you will have to migrate over to using IMS integration.