No, I would not say that VCSA 6.5 does not support Horizon View, it is more about the database setup. VCSA uses an internal database to store inventory information. Horizon View needs to connect to an external SQL database to store event information and Composer (part of the view deployment) needs to create a coposer database as well on and external SQL database. These components of Horizon view currently have no capability to create their own internal database (postgre or otherwise) the way that VCSA does. You may be able to connect them to the postgre database but I have seen that supported or done anywhere.
So if you have a Horizon View deployment you already have the requirement of an external database, windows sql or oracle. Since you already have one in your environment, deploying the VCSA doesn't save you the trouble of setting one up.
I hope that explains my position.