- The boss will not ever swoop down during its last stage (>75%).
- Rows of comets are spawned on a regular timer.
- Any swoop that has already started cannot be cancelled.
If you put everything together, there is an edge case where the swoop starts at <75% and while it is in progress the boss goes >75% and attacks with a full comet row. In this case it is indeed possible to be trapped.
However, this can’t be easily fixed. You should just be mindful of the 75% mark to avoid these cases. Given that the boss only swoops in difficulties >100%, I think that’s a reasonable expectation.