Oh... I am running Ubuntu 16.04 LTS
I have the same problem and I agree that it is unexpected: why would "tsm stop" leave any processes alive?
I tried killing them all but they just get replaced
Amazing that such a basic question even needs to be asked!
I found a way:
First, check the name of systemd unit process:
# systemctl list-units | grep -i tableau
user-999.slice loaded active active User Slice of tableau
Then stop it:
# systemctl stop user-999.slice