We are currently working with a headless approach and I'm trying to
estimate pros & cons of having more selectors in addition to 'model' at
the cq:Page component. After digging through the request log and
basically discovering what @Jörg_Hoh also mentioned here:
some special magic included within the cq:Page component redirects
requests with special selector 'model' to the page-content where ...
I had some trouble while using Sling Resource Merger & includes too (in
6.1 though). From my experience I can say: don't use both together!
Either use the Resource Merging mechanism or includes separately.