EDIT:

My horrible, ostentatioous BAD! I mixed up the GE headline with the viral United Airlines tweet about the same exercise:

https://twitter.com/united/status/1466045020473942020

In which they took care not to mention the second engine using standard fuel, going so far as to say (this time quoting correctly):

  Today, United will be the first in aviation history to fly a passenger flight using 100% sustainable aviation fuel (SAF).  

  This flight will serve as a turning point in the industry's effort to combat climate change.

So I definitely should have read the GE headline more closely (which doesn't make this obfuscation). But that's what happens when these companies keep lying, and lying, and lying - at some point your senses go numb, your eyes start to bleed... and you lose track of detail.

But at the end of the day - my bad!

Earlier, ill-thought transmission (from me) follows below, as-is:

  The point isn't the testing protocol, or that two different fuel types were used.

  It's that these companies are trying to play with our heads.