Like Scott Manley says, going from a frequency domain image representation to a time domain sound file is something that is extremely old and does not and has not required AI the last 50 years. It's just that they vibe coded the extremely old, extremely normal algorithmic solution. AI did not recreate the dead pilots voice, it just made data preparation and coding a bit less work.

It's almost certain you've used software or seen/heard software output today that transformed between frequency domain and time domain. It's ubiquitous.

Why did they need the spectrogram?

Not everything is AI, they provided the spectogram. Even a trained eye can read one, especially if context is provided.

Grisly, but I’m against restrictions on releasing what should be public information. Even if they came from the 1990s.

These knee-jerk reactions, creating special case rules, really seem like a negative to me.

Just wait for a ban on posting dash cam or police body cam recordings.

A spectrogram is literally the same audio, just transformed through a Fourier transform. That transform has a trivial inverse. The spectrogram isn't perfect - the visual representation is low resolution and the phase information is missing - but it's plenty enough to at least figure out what was said. There's nothing surprising that this is possible, only disappointing that whoever published the article didn't realize it.