its all about termination, not branches 

Branches are not always a problem.  They are the problem when they are long and not terminated .

If the unused branch was terminated, there would be no  echo  to cause the problem. 

Its a little confusing, as its the AC impendance , at the tail of the branch, and in the frequency range of interest that  would be  deciding whether its  terminated or not, it could be terminated for one frequency and not terminated for another. 

But The main point is that the  lack of the device on the unused branch  that  is causing the echo.

any moron can see that the branch with the users device on it could also cause an echo, if branches cause echo, all three branches could cause echo ! What is the difference ? the lack of a device on the unused branch ! 

also , The "signal travelling down the branch" is no problem of it self - 
its the coming BACK that is the problem !

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