I wonder if you were able to jump off it[figurine] reliably during gameplay, or if it was just something you noticed in the entrance room.
I did it a couple times, to middling success. It also saved my run when I thought I soft locked behind the green pooled wall.
About the room you could not exit after you ran out of mana - you can reach the ledge if you crouch jump from vines to the left of your screenshot.
Now this I didn't expect. I never thought that you could crouch on a vine, the concept sounds foreign. If anything, I would assume crouching would lower me down. Maybe it is explained in the tutorial, but I didn't play it this time around.