Earlier quoted context omitted.
I don't quite understand what the risk to coinbase is if Satoshi is alive/identified? Do they think he has a hack or something?!
If Satoshi is identified he might also still be alive. This means that Satoshi's BTC (~1mio.) are potentially liquid which would mean a gigantic influx of fresh bitcoins. It's quite plausible that any movement of these old wallets would crash the Bitcoin price for quite a while.
There's no way to absolutely sure that the keys are gone and inaccessible permanently.