Unused graphics: Knuckles' button?

Here's another one from Angel Island Zone. One of act 2's PLCs loads the following graphics to VRAM address $8700:

The first eight tiles are used by the background trees at the very end of the stage. The last seven tiles, however, cannot be seen in-game because they're instantly overwritten with the graphics for breakable floors.

No sprite mappings for these tiles seem to have survived in the final game, so we can only speculate about the object's intended appearance. However, by applying the player palette and arranging the tiles into sensible shapes, we arrive at the most likely configuration: a button.

Now, since these graphics are loaded at the start of the stage, they could have been meant for anything. But taking into account that they're included in the same art file as a tree sprite which only appears at the very end of the level, we can probably assume the button was also meant to be used near the end of the level.

Another clue comes from the graphics themselves, namely the blades of grass at the bottom, which are rendered using Tails' colors, no less. Normally, it would be unnecessary to bake the grass into the sprite like this: so long as the sprite's priority flag is clear, the object should naturally be drawn behind the level blocks.

The exception is at the very end of the level, where the background waterfall blends directly into the grassy floor. In this scenario, when a sprite's priority flag is clear, it gets drawn behind both the grass and the waterfall, and when it is set, it gets drawn in front of both. Baking the sprite is the only way to make it show up in front of the water and behind the tips of the grass which, you guessed it, perfectly match Tails' colors at this spot.

So the button was likely meant to be placed at the waterfall, possibly making it a precursor to the one used by Knuckles to drop Sonic and Tails into Hydrocity Zone. Here's how that could have looked: