+1 @tonywinga
You are balancing boundary reinforcement (getting close to the walls), with SBIR (cancellation from front wall reflection), and room modes. @bigtwin , Focal appears to be attempting to at least balance some of that in their formula, but as you noted, it may result in unrealistic values for many listeners.
@sc2, it is a little more complicated than what you have indicated. The distance they gave you appears to be to be outside the 10msec critical early reflection time. That may add a low frequency bass suck out (~50Hz). For many, even with a dedicated listening room, that may be too far into the room. That gets us back to the speakers being closer to the front wall, the front wall heavily treated for reflections, and using equalization to address boundary reinforcement.