In my understanding the draft takes a balanced approach.

The blockchain will not be rolled back, however, its interpretation may change.

The blockchain is immutable [...] not necessarily to the interpretation of that data.

In case of an actual bug (i. e. the implementation does not match its intent), remedy is possible.

The scale of the bug matters.

Immutability is a high good, but it's not the only one. It may have to be sacrificed for higher goods. The if/what/when must be decided on a case by case basis.