When you're one room away from a save spot, it says "Hey! There's a save spot here!"
Why is this good?
It prevents you from walking RIGHT PAST the save spot that they cleverly put next to the boss, only in just the right position so you could barely miss it.
(In fairness, there are other ways to do this too, mostly indicating that a room is a boss room *before* you go in, and that's something that Super Metroid/Metroid Fusion/most of the recent Castlevania games got right. But this is a really nice way also, and prevents you from knowing *exactly* where the boss is - the save room is nearby, you know that, but the boss might still surprise you a bit.)