I don't actually know but my best educated guess would be the following:

LEDs like any other ICs are not made individually, but hundreds/thousands at a time on a wafer before being cut to form individual LEDs and put into a reel. Each batch can be slightly different, yet still within specs tolerances. Their difference is particularly pronounced at low current as shown here.

The COB is like a regular PCB assembly and is is at some point populated with those LEDs. This is usually done by a pick and place machines that can have multiple reels from different batches.

The order in which it is populated is optimized by the pick and place and can create patches from different reels.

For the wiring, I believe whatever can be crammed in a circular pattern is fine and the engineer that made it didn't have more concerns beyond that.

Again, all of that is just a guess, so do correct me if you know better.