I'm not sure whether this is a bug or not, but this behavior is making notnotmelon's Factorissimo 2 fork crash.

Oooh, that's an interesting problem. I've not been able to replicate the crash though.
What nuke did you use to destroy the building, and how close-by was it?
Also, can you replicate the issue with the indestructible setting off?
What about the "retain damage statistics" settings on true nukes?
Thanks for the report, I'm not really sure where the issue is yet.

It only happens when factories are set as indestructible, which only sets the indestructible flag on the entities so by manually changing that flag in the editor you can test and change the outcome.

The nuke only needs to deal more damage than the remaining health of the factory, despite the factory being marked as indestructible.

To reproduce this you must:

1. Create a factory having Factorissimo's indestructible setting on (or through the entity flag)
2. Place an electric pole which covers the factory, and it must be in the south (forgot to mention that one)
3. Drop any nuke that would destroy it

I couldn't avoid the bug by disabling any options of True Nukes.

Ok, I didn't know the power pole step, I'll try that now

Awesome, I found the issue, and I think I've fixed it, though I can't be certain there aren't edge cases, as factorissimo has lots of hybrid buildings, and there may be cases where the overall destructivity of the weapons can break that.
Still, it worked in the test case I used.

I can't reproduce the problem any more so this is “fixed” despite not being a bug. Thanks for the fix.

I'll happily class it as a bug, as T-N was destroying indestructible entities, so yeah, fixed.