I've been thinking about the data for Heavensward and I'm trying to understand how this will work. Let me know if I'm off.
There are 2 versions of HW: digital and physical. Both come with codes. These are keys allowing you into HW areas. You plug that sucker into your Mogstation and there you go.
Patch day will give everyone, including players that didn't buy HW, the assets and data and things. All you are essentially buying is the key to get in (and in game goodies).
Physical buyers have a CD. This CD is used to install some files into your machine so that the patching takes less time. The digital people have to suffer through all the files.
Is that about right?