That feels like a failure of communication by the movie if that's what you got, because in part 1 she knew that she'd possibly given birth to the Kwisatz Haderach, and she'd know why that was significant. Did the movie give you anything on the Kwisatz Haderach as a separate entity from the Lisan al Gaib, or why Paul (and later Feyd) was so important to the Bene Gesserit?
I get that mom "believes" that Paul is Kwisatz.
But from what I can tell Paul and the rest of the bene gesserit don't believe that Paul is that person.
It seems more like ay slim possibility at best. If the bene gesserit believed he was Kwisatz why would they try to help orchestrate to have Paul and family killed.
And the movie tells me that Lisan al gaib is a fabrication by the missionaries. And Paul seems to mention as much numerous times I'm the films. So I would say yes Lisan is different than Kwisatz.
My point was that me as a viewer. I don't need to know all the answers and background. The movie was extremely compelling in the story it told and it left space to later develop. So for example if part 3 comes and they explain the science of prescience then fine... If part 3 comes and continues to treat it like magic... That is also fine for me.