There are probably thousands of people qualified to verify a vowel quality in a sound using a spectrogram. This would be one.http://www.cog.brown.edu/people_lieberman_personal.htm
It's a basic tool to visualize the resonances in a sound, where measurements can be taken. I'm self taught using information on line. It's up to you if you want to dismiss it , but you should try and verify my observations instead of using hand waving and opinion. Which I'm sure is your next point of argument..
I've already posted the information from the professional linked above on how to do it, But it seems you haven't read any of it, or attempted to understand it. There is terminology to become acquainted with as well as practice in identifying the elements of sounds the terms refer to in the spectrogram.
Here's a tutorial.
In part , the same way you've arrived at the conclusion it is a Lynx. I hear a hominin which not only achieves a salient vowel /a/ but also has the breath control to maintain a steady vocal over several seconds. The absence of any other cat sounds is also informative, particularly the growling that precedes the scream in the Lynx recordings.. The voice cracking is also so much like a human and unlike a cat that I almost can't believe I have to explain it to you.