Well I do not use syncing like that. So I have no idea how TC or other do it.
Problem is like I said, syncing is different for everybody. different people want different things. less and more complex.
You for example want it to delete a files/folder that was delete on one of the location.
Now things are getting complex, Now we need to hold some sorted of database or something to track the state of what the original state was.
and if you do multiple machine/drives things are getting even more complex.. And that is only one case.
Problem is that there are so many corner cases with syncing and I do not have the time if find them all, and figure how how it should work in all of them.
I would take me months just to find out everything it needs to do, and how it should work and such. I don't have that time.
The time I have to spend on MC is limited, Too much work to do my self. Sorry.
There should be lots of free 3de party syncing tool. Alternative way might be to add something so MC can launch and call them. maybe