It's cash settled based off the price of an index, which makes it easier. They just defer to the folks making the index.

If it was physically settled you could squeeze the shorts by having a last-minute unilateral grant of a side-token to everyone who possesses the underlying. The shorts have to come up with the token or cover the contract - either way, you have people who are forced to buy it to cover contractual obligations, and you probably own the only exchange capable of making transactions with NewToken (and maybe also you pre-mined some of bonus tokens to sell?)

When its cash settled, this is much less of an issue. No market? No market price, so it doesn't get included in constructing the index.

Probably not too differently from how equity exchange products deal with corporate events like mergers and spinoffs.