The coins are not actually moving as stated in that article. It's just manipulation dust spam.
They aren't moving
YET. Article says FBI is considering sell off within coming weeks.
If they are a currency then the BTC are seized cash assets which would not be exchange to another currency.
This is because if the trial finds him innocent then they would have to return the currency as the "account" was frozen at the time.
If they consider the BTC to be an "object" with value then again they cannot just sell them for USD since they would be considered evidence.
Afik assets/cash seized in more traditional cases have sat static for years due to ongoing cases.
So no I don't see anything being sold anytime soon and these BTC will sit in limbo until a vertict is reached.