As far as I know, Arkham is not capable of deanonymizing coinjoins. They are an explorer that can tag an address based on certain patterns, like an address that gets swept into Binance’s cold wallet can be assumed to be a Binance deposit address. They automatically tag many addresses as coinjoins addresses, but there is a flaw in their algorithm that sometimes mislabels addresses from batch payments as coinjoins addresses. Even if they can identify an address as having participated in a coinjoin, they can’t tell you anything beyond that unless a participant does something to compromise their privacy, like coinjoining to a reused address.