I'm going to make a prediction.

The core team will migrate some huge chunks of their own funds without an opt in because they lost the keys.

I think that's the real reason they are doing things in such an obtuse way. They lost access to a bunch of coins, and instead of admitting they're gonna fork to get it back, like ETH, they'll lie, and break backward compatibility to cover their tracks...

If they admit they can just fork to take back coins, then it makes them look even worse for not solving the coincheck hack that way.