Erwin !
You are one of those who deserves a prize for your efforts alone.
Maybe it even deserves me working it out (after all). In any event you're a man to my heart with those (Taskmanager etc.) details.
All right - I only read this minutes ago and I must digest it (and read it again a couple of times).
It feels a bit like Android doing the trick here, because that allows formally for playing offline. ... I don't even know how formal this all really is, and to what degree it is actually known that it can work like this. What do you think ? is this known indeed, or did you just found out yourself ?
What's comes across as odd to me, is the (not-) streaming part, which would go unnoticed. Thus, who would know or see the difference, unless you pull the cable ? But careful, because you pull the cable of the control point (which would be Android in your case) and you did not put the Ethernet cable. I think you showed sufficiently you could do that as well, but you did not do that and also did not contemplate that (IIRC after reading all one time). Or did you ?
On a side note, in the last version of XXHighEnd - which contained the special download for Tidal personnel so they could check the working (which never happened and instead I was kicked out), exactly that happens; when playing Attendedly, you (Erwin) would be able to show exactly the same, with no hiccups between tracks. As if it was streaming, but it still was not. Thus exactly your story, hence I surely understand and how it could work. Btw, similar to what Audirvana does from its start - telling that it plays from memory while it takes a minute to do so, in parallel to playing itself. Read : that *thus* does not work (out) at all and sounds poor. Only XXHighEnd really plays from memory (say a full album) without any further intervention.
... But I would be able to let it work, at least when not gapless is allowed. You'll understand. Or other trickery I can't oversee yet.
So I will need to dive into this - and like to. The when is more problematic these days, but we'll see. If you have to spout more meanwhile, don't hesitate.

Peter