That's
DarkStar_'s address, not ChipMixer's.
It's not as if Signature Campaign addresses aren't public anyway.
this is a easy point to link back to their other wallet because they use the fees of swaps to pay their advertisers
That address gets funded from the same chips ChipMixer uses for any withdrawal. There is no "other wallet".
You can even
make your own chips:
you won't even need to use mixer to anonymize your coins. Just split them into tokens and they look exactly like chips.