Ok. Here is my file.
Let's asume we have lines A,B,C,D,E,F,G,I
Lines D and E are tight with Tangent constraint.
If I move E or D, or any of their points, only C,D,E,F lines are affected (and if we take their points, then add B and G to that list)
And at least A and I are not affected at all. And now imagine a long chain of unneeded dependencies (or whatever) calculated every time I do something
In example I've provided only one constraint is present. But you can even remove it to, then do something and you see what Im talking about. I can drag any point where ever I want but if I release it - FreeCAD goes into DEEP freeze
P.S. Yes, It's a Horsie