This paper is an example of pseudoscience masquerading around as a thorough scientific investigation. It really is not. Reminds me of ASR.
The methodology is cursory and full of cliché. Anyone attempting a serious evaluation would center around comparing a large number of tubes and extensive listening with a high end system... Observation would be the key... not measuring a couple parameters, saying the designers would know and only putting one comment on a blind A/B test... "“blind” A/B audio testsrevealed no tonal differences or improvements between the treated and untreated tubes. The amp didn’t sound more “holographic” or “possess more subtle inner resolution”; and, unsurprisingly, it wasn’t any quieter either. This result was not unexpected." Also, embedding a bias towards not hearing a difference.
To me, this paper says nothing. It does not show that Cryo improves, does nothing or degrades the sound. It is just a puff piece.
I would be really interested to hear from any folks here that have compared cryo to non-cryo tubes. I would be really interested to hear the results.