In the end, I decided to keep the Solitaire P. It is a demo unit, so I got a good price offer / drop on it plus the VAT drop in Germany. It is not going to replace my D8000 Pro or D9200 (replaced Stellia, which costs about double its price). I have been listening to different recordings since Friday, also invited the third player, D9200, in the game.
There are scenarios (and temporary preferences) that doesn't benefit much from the large space and might make some instruments sound iffy, in which case I prefer the more tight envelope of D8000 more. It gives a better texture feeling, but actually in real life and live listening one would rarely have this intimacy and well enveloped texture. Also there is a bit of more "air" with D8000 and D9200 which I can imagine might be a preference in certain cases, but this is also something more nitpicking which is more noticeable if you switch back and forth between the HPs, but the feeling subsidies in seconds. For example this little piece from Alain Perez & Omara Portuondo album ADN, one might prefer the D8000 / D9200 sound (side note, I cannot believe Omara was over 80 as she recorded this and have this control over her voice):
I think main question could have been, how the vocals will sound. I tried different well made recordings of Cecilia Bartoli, Ghada Shbeir, and female vocals actually rendered extremely well which does not need the unnatural extra push of Focals. I mainly listened to my wife's album and had her listen to it (she just hates listening to it), who is a Stellia fan, and she was very impressed with the rendition. For example, with this piece, it is easier to hear some nuances with D8000 and the vocals pop up more, but with the Solitaire P, you are inside the room, and all the bowed instruments are rendered more emotional (the "strange" instrument you year at 0:14 and 1:41 is called a singing saw):
The subtle back vocals merge better with the main vocals here.
I don't think it is lacking any details. On the contrary, it can easily fill up the space with reverberations and harmonics. But as said, this expansive sound makes the mixing issues related to locations and recording space differences more visible. It is not a "throw whatever you want at it and it will sound as good" HP like D8000 Pro.