force function object has no control over output frequency in postProcessing folder

I am not sure if that is a bug or a feature request and I have not tested enough to identify all possible options (I did test in both v1906 and the latest plus version), but it seems to me that:

• no matter what I write for writeControl and writeInterval in the function object definition (forces in this case, but I think it applies to other function objects as well) the output in the postProcessing folder is always one per timestep

• the same applies to the "timestep"/uniform/functionObjects/functionObjectProperties folder (ie: it gets written when fields are written no matter what I write in writeControl and writeInterval for the function object.

A simple test can be made using the $FOAM_TUTORIALS/compressible/sonicFoam/RAS/nacaAirfoil tutorial with this modified controlDict. I modified it as such: made the fields write at each timestep and requested an output for the forces function as such:

        writeControl    timeStep;
        writeInterval   10;

but the output in postProcessing/forces/0/coefficient.dat is still made every timestep and the field folders still show the computed forces for each timestep, as can be verified by the following command: cat *e-0*/uniform/functionObjects/functionObjectProperties|grep results|grep -n ""|less