Hi Elina.
I looked through my archive of downloads, and you are insofar correct that the 700 mb image, at least back to 12.0, only ever contained the "messages" folder and in some (but not all) iterations also the REST documentation.
However, please allow me to summarize my understanding of what this means:
There are component downloads (several in fact) that are specificially designated
"Documentation", for AE, which do
not in fact contain
the documentation for AE, but contain only a lone, single and seemingly arbitarily chosen addendum. This, then, is by design.
I'm not even the original poster of this thread, that'd be
@Frank Muffke, a former Automic employee and a bit of a legend. If seemingly he (and also myself) can't make sense of that, I'm afraid my gut feeling for many of the thousands of other clients instinctively grasping this concept is less than stellar.
But all of that is, naturally, my €0.02 :)
Best regards,
Carsten