Yes, the thread is definitely valid. Just because CDPR doesn't want (or possibly know how) to fix persistent glitches doesn't mean that they don't exist. The Double Down description reads: "Whenever you play a unit from your hand, play a unit with the same Provision Cost from your deck. Your starting deck is doubled in size at the start of the match."
Nowhere in that description does it mention Disloyal units triggering and playing the double down unit from the opponent's deck instead of your own. In addition, the description explicitly states that only playing units from the hand will result in an extra double down unit, so Oneiromancy and Royal Decree shouldn't be working. Therefore, these are both 100% glitches, with no room for interpretation.
The only real disagreement was regarding what constitutes a card being part of one's starting deck. I argued that Assimilate shouldn't trigger off of any of the extra cards that get added when a player's starting deck is doubled before the match begins because increasing a card's quantity is not the same thing as adding a new card, but regardless of CDPR's definition of the starting deck, I think nearly everyone agrees that allowing the extra Assimilate triggers completely breaks the balance of the mode.
How often do threads like yours see any improvement in things, especially for seasonal mode? I've probably contacted support at least once on badly worded aspects to the game. It's a fine line between being tricksy, e.g. the scorch card, and just being badly worded. CDPR probably tend to the latter more often that not, I suspect. Anyway, I'd agree with your point about assimilate. I was wondering that maybe, to draw a long bow, you could say that having a card in your hand which allowed you to play a unit might possibly allow for putting another unit of the same provision cost but if that's conceivable, I suppose that the question is whether that applies to the provision cost of the non-unit card or the provision cost of the unit card which the non-unit card has summoned, so to speak.
In any case, I didn't play that seasonal mode much. Haven't really been interested in playing the latest seasonal either. Occasionally I like some of those modes. I hated the one from last year where that Nil deck allowed one unit to constantly spawn, the unit which repeated your leader ability. What's his name. At that point I was too scared of wanting to try that deck for myself, thinking I'd muck things up.
I'm pretty much over this game but I suppose that I had a good run with it, playing it since COVID became a thing. Think I'll try and write a review of it on GOG soon.