We have done few customizations on personalization components in AEM 6.3 . The details are as below :
1) Created custom AudiencesServlet by resourceType pointing to custom project ambit page with selector "audiences" and extension "json".
2) Overlayed target component in apps and modified engine_cq.jsp to change the default.json
When I run pattern-detection on aem 6.3 instance, it was showing "Extraneous Content Usage" warnings on the above mentioned customizations.
Also the folder /libs/cq/personalization/components has jcr:mixinTypes marked as granite:FinalArea and the above mentioned customization's supertype are located under the same path (/libs/cq/personalization/components/ambitpage and /libs/cq/personalization/components/target ).
As per the documentation available on sustainable Upgrades, (Adobe Experience Manager Help | Sustainable Upgrades ) , "Nodes classified as final cannot be overlaid or inherited. Final nodes can be used directly via sling:resourceType. Subnodes under final node are considered internal by default".
The above customizations are done by overlaying and inheriting the super types and hence would like to get some pointers on the solution front.