Sonic 3 & Knuckles unfinished/hidden area

I was exploring S3&K as Knuckles when I stumbled upon this area. Apologies in advance if someone already found this.

It's in Carnival Night act 2, just before the boss. There are the vertical tubes that Sonic/Tails would fall down, then face Knuckles, who would activate the tubes and suck Sonic up into the boss area. Obviously this doesn't happen to Knuckles.

So you climb up the tubes (left side for the bottom one; if you reach the top on the right side, you will fall) to the boss area. Heading right would trigger the boss sequence, but you will want to head left instead and climb to the top of the left wall. Glide across the top to the right wall, and you will find some tunnels leading right and down.

The first tunnel (on the right, as you climb down) leads to an apparently-unfinished area of the level, devoid of rings and badniks, with non-working objects. It's quite possible to get stuck here and have to wait for time over.

The second leads into an area resembling the Act 1 boss area. Falling down the far left side of this area lands you in a wall, where you can jump/move around and be "teleported" to the robotic egg. Opening it ends the zone without fighting the boss.

I've found other areas like this in this and other Sonic games, but this is the first I've found that's accessible without the debugger code (though it's inaccessible in plain Sonic 3 because Knuckles's climbing and gliding is required.