First and foremost, session activities need to be consensual. That said “humiliation” and “forced” are similar. I think they are both used to imply someone wants to push things (within reason). With regards to FT, taking a dump on the sub would qualify, but what if she then rubbed it all over his face? That might qualify as humiliation.

In reality they are both words that mean “I want to partake in activity that ‘normal’ people would consider crazy”. One activity I can’t get enough of in a session is being spit on (or in my mouth); something that out in public would be truly humiliating .

They’re both code words, but instead of asking for either of those it is better to come right out and tell her what you are looking for (ironically, for some that could be humiliating).