Philippe, did you use Fomabrom 111 or Fomabrom Variant 111? Just asking, because I get that warming effect as well when using Fomabrom Variant 111.
It is the Variable Contrast (Baryta) variant I use...
Perhaps this might be an indication: the developer I process this paper in is home brewed E-72 {2 à 3 min at 20 à 22°C (thermostat set at 21°C}) which is a human friendly variant of the famous DEKTOL.
I have the (very personal-) impression that the type of developer in which the paper, regardless the kind/brand, is processed, could determine whenever the Selenium treatment will or will not change the image colour and D-max.
For a short while I developed the FOMABROM FB in Fomatol P (due to Phenidone not being in stock) and the image colour, after my usual Selenium toning, wasn't that "neutral-to-coldish" and the D-max was a little less.
Also, when on the rare occasions I develop the paper for twice or three times the usual time as I really wanted very deep blacks, then the paper doesn't change colour nor the D-max 'deepens' when Selenium toned.
PS: I looked it up and the real way to write 'maximum of optical density' is 'D-max', no capital 'm' and a hyphen...