Write interval in forces function object

For the first time, lately, I had the need to write forces with a specific interval and realized whatever value I used in writeInterval, the output file in postProcessing had the forces written every timeStep.

I then spent a couple of hours trying to figure out if something was wrong in the function object input in the controlDict as well as trying to use old releases to see if something had changed or if a bug had occurred.

I then came across the issue #1642 (closed), and I believe, as an experienced user, this is very confusing.

In the referenced issue, it is mentioned that "The writeControl entry for the forces function object only controls the writing of the volume fields" and therefore the output must be controlled via executeControl and executeInteval.

In my humble opinion, or from the user point of view at least, I don't see the difference between the forces computed as the integral of pressure and shear over patches via libforces, where the output is controlled via execute-type controls, and the average values of pressure or any other variable computed via the "libfieldFunctionObjects, which is controlled via write-like controls instead.

Maybe the handling from the coding side is very different indeed, but I'm pretty sure no one out there would have figured that out plus there isn't any mention to it in the official documentation.