It's definitely interesting if the concept is new to you, but there's quite a lot of work on this done already, decades ago, which should be known to those who care about securing airgapped machines. Here's a good place to start: https://en.m.wikipedia.org/wiki/Tempest_(codename). I did a demo as an undergrad ~10 years ago playing music on the radio via leaked emissions from my netbook. Didn't have to write a line of code because a complete solution had already been freely available for quite some time.

It's not without value, no, but they've definitely found a formula and are just cranking out variations of that formula as papers. I'd say calling it a paper mill isn't too harsh.