If there's reasonable suspicion that your profits can be linked to the criminal activity (for example, you might have been a money laundering accomplice of the drug dealer), why not?
In any investigation concerning criminal financial activities, accounts are frozen until it has been determined what funds are criminal gains, and what funds are "innocent" money that just happens to be parked in an account. Like it or not, this is pretty normal and has nothing to do with the fact that in this case bitcoins were confiscated.

In the SR case, determining which sums are legal and must be returned to their owners might be difficult - I somehow doubt that DPR earmarked the funds with a legal/illegal flag.

Onkel Paul