You are saying my body proportions are weird? ;-)
I agree, the -17deg 150mm stem does seem a bit odd.
There is an explanation for it, though.
I went there to get a fit on my current bike at the time. We ended up sliding the adjustable stem out to 150mm before realising I couldn't achieve a proper fit on it (frame was too short), I was then moved to the fully adjustable retul bike and got a proper fit there.
To save time, I guess he did the adjustments on the frame and not the stem.
However, It does not bother me too much. I look at handlebar stack/reach instead and use online tools like yojimg.net/bike/web_tools/stem.php to calculate stem length and spacers when browsing frames.