Thats a fair (no pun) question! The reason "source available" exists is to starkly seperate it from "open source", yet to your point, they certainly can be both. However it is reductive/pointless to say my code is "open source and source available" since of course the source is available if its open source.

This highlights my knee-jerk reaction to your initial post. My original definition I provided for Source Available was "[viewable but not OSD]". This is overly restrictive since can be both, but to assign any meaning at all Source Available it needs to be defined in relation to "Open Source", otherwise its meaningless.

I agree, it really isn't complicated :).