They just exist to extend the floor collision. The crusher works just fine without those invisible blocks.
A more detailed look on the unused swinging platform object in Sonic CD v0.02 (object 0x29): While not placed in the stage, its graphics are loaded in act 2 around the area in which a swing is placed in the final. The number of chain links it spawns is determined by the lower 4 bits of its subtype value (0 = underflow, 1 = 0 links, 2 = 1 link, etc.). The upper 4 bits determine how it moves. There are 8 unique movement types: 0x - Moves in a circular motion clockwise. 1x - Moves in a circular motion counter-clockwise. 2x - Moves 180 degrees downwards. 3x - Moves 180 degrees upwards. 4x - Moves 540 degrees, starts facing west. 5x - Moves 540 degrees, starts facing north. 6x - Moves 90 degrees downwards. 7x - Moves in a circular motion counter-clockwise, and also spawns object 0x13, which is a Mosqui in Salad Plain. It is unknown what the object was intended to be (maybe a switch?). It was speculated before that it was meant for Tidal Tempest, but the fact that the graphics do load here say otherwise. In fact, the final swing object in Palmtree Panic also features 8 different movement modes, while the one in Tidal Tempest only has 2 movement modes, both moving in circular motions. Really, the idea of remnant objects from other zones in v0.02's R1 doesn't really work out when you realize that Sonic's movement code references the Collision Chaos pinball flippers by object ID, yet the actual object is not found in the v0.02 build. Also, the Collision Chaos remnants in v0.02 are all within Sonic's object code, which makes sense, since it's shared between stages. Also, in v0.02, a pre-v0.02 FM sound driver can be found in the stage files, and they contain an even earlier version of the time warp sound.
I've received a few comments on Twitter that compared it to Sonic Spinball among those commenting on how dreadful it sounded, so you're not alone there.
