Firstly, so we all know what we are talking about:
So these are often really low-run discs, almost in similar vein to DIY cassettes or CD-R’s.
Considering the way these are produced (often I believe for demo purposes), are they really Official or more akin to Promotional or maybe some other release status?
Well, depends 
If they are official, they are official - some bands have had official CD-Rs too.
It reminds me of the discussion about test pressings. In most cases it will be something similar and even if it doesn’t exactly fit into the “promotional” category, most acetates will probably belong there.
I don’t know about acetates, but I’ll mention that lathe cuts are often/usually “official” releases, since the two are often confused.