Well, I asked that because recently I read
one paper centered on analysis of tainted bitcoins authors of which have concluded that using small amounts of "bad" sats criminal may poison the innocents addresses. Their thought sounds like this - "a criminal who knows how the approach works might just send tiny fractions of Bitcoins to random addresses to taint them" . So, criminals knowing that all their
BTC are tainted and having them in enormous quantity can intentionally contaminate as many addresses as they want in order to conceal their own addresses among all others.
The definition of 'tainted coins' are not defined strictly. Depends on how you define 'taint', you can classify those addresses which has received tainted coins to be part of that 'taint' or to consider it based solely on whether that specific UTXO has been associated with the tainted coins. Bitcoin addresses are recommended to be a one use address and unless the criminal wants to waste substantial amount of Bitcoins to taint, and AFAIK most don't consider addresses with dust spam UTXOs as tainted, it wouldn't be of much use.
The concept of tainted coins, tainted address is just a way to make Bitcoin less fungible and I do not agree with that concept at all.