Therefore "taint" from the real world's viewpoint is real, and because Bitcoin is easy to track, each Satoshi has a "history" and a "context" because any entity can put "taint" labels in them.
"Taint" is subjective. The objective viewpoint is to treat every coin equally, just as you would with cash. The ledger provides coin history, but beyond that it's utter guesswork to determine who owns it, what was exchanged etc. But, deeming mixed coins as "tainted", which is known practice by Coinbase, is insane. You cannot even argue the coins have "bad history", because it is completely erased in the first place. Mixed coins are indistinguishable; deeming them "bad", just because there is an x probability of being owned by a criminal is insane.