it was more like a swap than an option, especially as there was no optionality. The sale was binding, with only the closing date variable in one scenario.

There still is a kind of optionality. The TIME optionality. And indeed it is more like a swap. This is why I said "close to an option" because it isn't exactly like a traditional option.

The ratio rose to 30

As an example of the time optionality, when it was trading at 30X, you could have simply locked in your profits ("optionality" to lock in) by selling Berkshire short (or perhaps using Jan '25 options if at a lower cost) and buying 15 bitcoins. Then come Feb 2025, you deliver the 15 bitcoins and they deliver the Berkshire share, and thus ends the transaction. They, of course, also have optionality of the same sort. When you think about it, because the transaction can be "closed" anytime you, or they, wish, the 3-year time period is essentially moot. (I think)