As promised here are some explanations from Sequential regarding this problem.
Sorry Sequential team! I was being little bit stubborn on this but... as I explained I pay a lot of attention to details and if instruction says
"The OS version is shown on the main display upon startup, after a “6” is displayed" I expect exactly this to see and not some random symbol.
Here is answer from support:
1. If the instrument is showing 1.1.2 in the display when you first turn on the synth, it is on the 1.1.2 OS, as shown.
2. There are many processes that happen in the boot stage e.g., CV's being addressed, processors coming up, etc.. If the instrument boots every time, it is working properly.
3. There would need to be a discussion regarding all the processes in the boot portion of the synth and as we are a very small team (22 people total), our engineering and software crew would not have the cycles to address these technical aspects of the boot process.
Checking out demo unit here at the office, it too shows the half plus symbol you are experiencing upon boot up.
So I would say that someone overlooked this '6' when implementing new things in later OS versions (it was showing on my device with 1.0.1 OS but then I have updated directly to 1.1.2, not sure if this was a problem also on 1.1.1?).
It seems that problem is quite common (if anyone on 1.1.2 does not have this issue please let me know!). I have even spotted that on Trigion-6 on one of the latest Doctor Mix youtube videos with Trigon-6 (see on attached picture ;-) ).
Well, the only thing missing from Sequential's response is something like 'yes, we have overlooked that minor problem, we will try to address it in future' Or some info that they will correct update instruction to not confuse new Trigon-6 owners - especially those like me detail-oriented...