Following consultation with cryptocurrency experts, I sold BTC and BCH, not by an ordinary sale through the BTC/BCH exchange, but in a manner that would avoid affecting the market price, while ensuring the security of the transaction to the extent possible, Kobayashi details.
Which means OTC.
Which means OTC.
https://cointelegraph.com/news/effects-of-mt-gox-trustees-400-mln-sale-on-bitcoin-market
"Over the past three months, Nobuaki Kobayashi has sold over $300 mln in Bitcoin on two public exchanges. Some critics believe Kobayashi's sales put so many Bitcoin back into circulation, that the sales contributed to severe drops in the price of Bitcoin."
You can believe what you want.
I'd take the word of the trustee himself over some random crypto media article.
Also, many exchanges have OTC brokering services, so it's possible the whole "selling on exchanges" thing was mischaracterized based on that. He'd have to be very dumb to sell directly on spot markets too, which I doubt.