Early in my career, I replaced a lot of sewer lines due to root damage. Now, I just do the diagnosing and estimates...
When a root finds it's way into a sewer/septic line, it discovers an endless bounty of nitrogenous waste. That's food to the plant. The plant/tree, regardless of species, will put a tremendous amount of energy into building up that root to get more of the "goodness". It will eventually clog or split open the pipe it lives in.
Basically, the plumber's advice is, don't risk it.
Too much too fast to keep track of...