@stefano Here is something new for you to be upset about, though, which affects everyone, Linux, BSD, illumos alike. I have been upset about it for over 20 years.
Read ‘man 5 fonts-conf’ or whatever your equivalent is. Read it carefully under ‘FONT MATCHING’. What it says is that a font is not chosen as you wished, but instead RANDOMLY. You are only LUCKY if you get the font you wished.
And if you experiment long enough you will find this is true.
Fontconfig is unfixable and must be scrapped.