That would be annoying if true since she never met Yoda in life, and only being able to see people you knew as Force Ghosts is one of their unwritten rules.
That seems like a pretty flexible rule to me. Also Rey might have seen ghost-Yoda off-screen on Ach-To. Either way it’d be pretty easy to “explain” Rey seeing ghost-Yoda.
Also did Luke know “young-Anakin”? Hayen-ghost is is officially canon.