I think this person is just karma/clout farming badly and the screenshots are of some even more basic RAT.
Interesting that the malware author isn't using actual compressed audio (No idea why the Twitter poster seems to think wave files are compressed) I would assume that you'd want to transmit as little data to evade detection.
Although .wav files are, today, typically used for non-compressed PCM data (WAVE_FORMAT_PCM), even the original 1991 RIFF specification allowed for three compressed formats: mu-law, a-law, ADPCM.[1] These are all efficient to compute and I don't find it completely implausible that such low quality compression would be used. Modern .wav files may use the WAVEFORMATEX or WAVEFORMATEXTENSIBLE chunk, which uses GUIDs to identify formats. It supports the original compressed WAVE formats,[2] but also more modern compressed formats. Here is For example, here is Microsoft's list of sub-format GUIDs (includes MPEG formats and AC-3):
https://learn.microsoft.com/en-us/windows-hardware/drivers/a...
[0] https://en.wikipedia.org/wiki/WAV
[1] https://www.aelius.com/njh/wavemetatools/doc/riffmci.pdf heading "WAVE Format Categories".
[2] https://learn.microsoft.com/en-us/windows-hardware/drivers/d...