You don't think it looks like the coordinator is Sybil attacking Bob using Alice's coins?
If the Samourai coordinator suddenly turned evil, why would it make it apparent that it is sybil attacking? We have previously discussed that in a malicious coordinator scenario, the coordinator is paying themselves, so the coordinator fee does not discourage them from attacking. Also, the coordinator can select their own remixed coins for free. So, why not create Charlie, Dave and Eric, to make it seem as if many people are used as premixed inputs?