I don't expect a massive dump. I even think massive dump is an exaggeration. It will have an effect if sold at once, of course, but Coinbase handled $1.2 billion in BTC/USD alone for the past 24 hours. So, $131 million is not even a tenth of Coinbase's BTC/USD pair.
Also, Coinbase has Coinbase Prime, their OTC exchange where institutions are making deals probably in hundreds of millions, if not billions. This amount coming from the US government might end up there. In which case, it won't be shaking the market much.
You're right, they didn't sold it at once so I guess they're also having that problem that every holder is problematic with and that's about selling in batches because we have no choice as the exchanges will question us. But this is not a problem to them, there is a tendency that they're doing it in batches so not to get as much attention that it will be but if that's the reason, they're not good in hiding as they've been already found out doing this massive tx.
Yeah, they liquidated those coins in batches. It might not have been out of care for the market; it could have simply been their desire to maximize the proceeds, or simply to stay inconspicuous. But they're not necessarily hiding all these things. After all, they will still file reports as to these activities. And these documents are probably not confidential at all.
So, I'm not at all bothered by this $131 million that would hit the market anytime soon.