Hi Juan, in my experience it is a compensating developer, and well,
according to ADOX, who currently produce it, It's a compensating developer by design."FX-39 is a compensating developer, providing excellent detail rendition, sharpness and resolution."
https://www.fotoimpex.com/chemistry/adox-fx-39-typ-ii-500-ml-conc.html
The recommend higher dilution for more compensation. I found it does that for me in the regular dilution. Again I am happy to not debate about it. He asked for opinions and I gave mine. I am glad that some folks like it!
I think there are two different stories here about compensation...
Clearly a developer can be designed to take good care of shadow detail: this is the case of FX-39.
Then, it can be sold as compensating, to interest buyers.
But real compensation is a different situation: it requires a very different level of dilution.
FX-39 gives wonderful tone for wet printing low/normal contrast scenes. Impressive. Contrasty and vibrant... Its best characteristic, as I did comment here before (post number 4)...
Although your two images look like scans (a digital photograph of a negative, resulting in new digital tone) and then it's hard to be sure about your negatives, both look slightly underexposed... Or who knows if just scanned for the highlights...
FX-39 gives strong, vibrant, contrasty prints from overcast scenes.
There are many examples on the web: that's why I started buying it.
Couldn't it be you didn't use enough developer, or enough time?
Hard to think Crawley was blind or people at Adox were and remain blind.
Just caring about young readers...