These tags have been bothering me for a while, and in Danbooru thread the discussion just got ignored and never reached any conclusion. So, here are my thoughts:
At the moment, cave & cave interior exist. They do not have any connection between each other in terms of aliases and implications.
In my opinion, there should be
a) cave entrance tag, as images from afar with the entrance being visible are tagged with cave as well.
b) implication from both cave entrance & cave interior to cave. Alternatively, keep cave entrance & cave interior & deprecate cave.
As an extra question that I asked in the Danbooru thread as well: Should cases where the location is inside the cave (like cave interior) but you can also see the entrance hole such as post #23550 be tagged with both cave_interior & cave_entrance?
Updated