If you keep a client in one project and each of their jobs in a sub-project, a fact you taught GPTree in one of them now carries to the others in the same family. Memories from another project are labelled with the project they came from, so the assistant knows where each one belongs.
In a conversation someone has shared with you, only that project's memories are used. Everything GPTree remembers is still in the Memory Inspector, where you can check or change it.