~snip~
It's exactly as you said it. The score remains from the moment that the address is tagged as "shady" or "blacklisted". The problem is that you can't get rid of it, no matter what you do. At least as far as I know.
Actually, you can, because mixers still exist for exactly that kind of thing, and there's also the possibility of swapping these so-called tainted coins for any other coin. What can be a problem is to send such coins to CEXs or some payment processor that will mark them as problematic and freeze them or, in the best case, return them to the owner.
This makes me wonder what is going to happen if let's say 70% of the Bitcoins in circulation are marked/tagged as shady or dirty. The would AML score thing is just going to make people fear using Bitcoin at one point for fear of having their funds frozen by exchanges because they acquired "dirty" ones.;
The idea of tainted coins is actually a weapon used by the authorities to direct investors to trade exclusively through CEXs, where everyone is required to do KYC. Likewise, the idea that the strategic reserves are filled with precisely such coins will be something with which the authorities will try to take their share of the pie without investing any money.