Well obviously the reason Leia doesn’t tell the characters about Lando is because they didn’t have the resources with her to convey such an idea. So that gets a free pass imo.
I would say the line “Leia sent me a transmission” conveys everything you need to know. Leia notified Lando, perhaps as a second thought, that the gang is coming to Pasaana. She likely knew that he had helped Luke with the search there, and sure enough he decides to travel there to help them.