>>48501426What he means is that you don't get unlock the whole cave at once (i.e. just getting Rock Smash), instead the cave is gated behind multiple HMs, so you either come back multiple times or you wait until you get all the HMs needed much later in the game and do it all at once.
1. You need Rock Smash to access the floor below at all. This lets you get a Stardust, a Big Pearl and Flash.
2. You need the Bike or Surf to get Brick Break
3. You need Surf and Strength to get the Earth Plate and Focus Punch
And while it's technically optional and you can technically wait until much later to do it all at once, getting at least Flash early makes navigating another area much easier.
