No; he clearly acknowledges that FLAC is lossless, so the audio is bit for bit identical to the original waveform.

The claim is that FLAC decoding digital hardware performs processing which causes noise ("computer hash") if it is not isolated from the audio paths. He gives an example of some hardware where isolation eliminates the problem, supposedly.

I'm skeptical of the claim. Not in the sense whatsoever that I suspect it being false (I don't), but in the sense that the same noisy hardware would produce some "computer hash" even if it were processing uncompressed waveform data. I don't know anything about FLAC, but cursory searches suggest that decoding it is very lightweight. Whether processing raw PCM samples, or decoding FLAC, the hardware would mostly be idle in between producing audio frames (unless it is an embedded processor that is very low in terms of computational power?)

Anyway, he's not simply an crackpot claiming that FLAC quality is inherently different from WAV.