I think, fixing of this bug is more important than it seems. Physics after readjusting/retouching "Trailer stability" slider is much, much better than default unnatural physics. For example, I didn't knew about this bug before, and I unsuccessfully tried somehow to improve this unnatural physics. Now, when I know about this bug, I have to change (with pleasure) some params in physics.sii like I want. It is very good.
Stewen, thank you!
Dear SCS, please pay attention to it.