My son friend in school have Tourettes. It my only experience with it so don't know if this friend is typical or not. Mostly facial tics but odd outburst verbally. He explain the more he try to control it, worst it is. He only swear when it happening and not normally in conversation.
It worse in High School than in Elementary but his family not swear so when he little, he not know swearing vocabulary because not exposed to these words to have. Used to say "poopyhead" and similar before Elementary. Cuss words got stronger in later Elementary years and the worst once in High School.
I trying to explain really that little kids who not heard strong cuss words, not have then to pull out when in middle of Tourette's tics which is when normally it happens. The f bombs have to have a source and have to be known to the child. It doesn't just happen that they magically know these words even when having medical issues were cursing is real symptom.
If you already have one client who feel strongly about cursing, or any other behaviors, you have to decide if taking a new client, knowing their child has this behavior is worth it. Sometime, if you have great client, it not worth losing them just to accept someone unknown into home.
Same if taking on child known to bite, punch, steal, etc.