Editing for clarity and ease of bug reproduction. Additionally confirmed in 21w14a. Additionally was able to confirm for 21w11a.
Perhaps a good test would be comparing the same coordinates of the same seed between 1.16.5 and 21w13a, that way the vein frequency/shape can be compared directly.
My testing seems to align with CrustiesAuto61, villagers can open them too.
Could you provide the world seed and coordinates of this abandoned village? It would be helpful for some people. 😉
Have you checked your volume settings in Music & Sound Options? I presume you have, but for the sake of being thorough.
What is your graphics quality set to? Fast graphics do this to help performance, whereas Fancy and Fabulous settings have transparent leaves. It would explain this if you were on Fast graphics.