That is partially true. The vast majority of money laundering is related to the drug trade, then probably organized crime in general .. with a good dose too of tax evasion, and folks trying to get trapped cash out of foreign holdings in countries where it is expensive or impossible to remove cash outside the borders.
Another part of this is how the US defines money laundering, which for the most part is something the Anti-Money Laundering Coalition agrees with.
To conceal or disguise the origin or destination of the money.
Historically terror funding has come from charities, where some front man will promote a charity (which they may even believe is legit) and solicit donations. On the back end terror groups siphon off money. Because the donations are to the charity for helping whatever the destination is disguised and that is laundering under US law.
One could make an argument that anonymized bitcoin transactions are laundering because sending them through a coin mixer or whatever disguises the source and destination. The law is more or less that generic.
This is not the only definition found in the statute, but it is one of them. There are also a few more elements but meh.
Charlie Shreem was charged with money laundering because he knew the coins came from TSR (or so count 2 alleges) and some of the transactions there are illegal in the US. This is one of the other definitions of laundering, promoting illegal activity.
The result is absent more specifics I tend to disregard money laundering charges because that does not mean someone actually knew what was going on. They might, then again they might not.