Well it’s never explicitly confirmed in canon whether Obi-Wan knew Yoda’s location while alive. I could just as easily assume he didn’t know it as a safeguard in case he was ever caught by the Empire and interrogated.
I’m also pretty sure that the current canon explanation for how Leia was able to contact Kylo on the Death Star wreckage is that ghost Luke taught her how to Force project herself in an instant. Dumb, I know. But it doesn’t stop there. The canon explanation for how Anakin becomes a Force ghost is that he is taught in an instant by Kenobi’s ghost.
It’s just a problem in Star Wars that you have to overlook one way or another. The ghosts are op (just like in the Lego games). And we’ve made them even more overpowered already because they assist in being able to kill Palpatine once and for all. I personally don’t see the harm in Luke divulging a secret about Rey to Leia so she knows what she’s getting into by training her.