But yes, if SH is banging on the ruin doors when you meet her on the beach she’ll explain that she’s hoping there might be something useful inside,
Ah, fair enough. I have always seen that door more as SoulsLike type shortcut, meaning I didn't make a mental connection between door below and ruin above. Getting there is a bit roundabout for me to connect the two until I emerged below after exploring the dungeon. As such I never assumed that player is meant to reach the ruin with intention of finding the space behind the door, but I think you are right.