You are looking for The Truth. Unfortunately, no one can say with certainty what that is. So like the rest of us, you are going to have to come to your own conclusions regarding this (and every other) training topic.
I would offer the following recommendation: When evaluating training advice/info, be sure to take into account whether the source is 'assisted.' The metabolism of someone on AAS differs markedly from that of someone who is not, and this allows an assisted trainee to successfully employ diet/training strategies that would prove deleterious for a natty. Not intended as a criticism of AAS use; just an observation.
My opinion: Fasted LISS cardio is not a problem re muscle loss; fasted HIIT might be. (I am unassisted.)
I've heard some caveats from proponents of fasted cardio. I've heard its only beneficial in the morning when cortisol is high anyway and FFA's are available to burn, and only to do low intensity (basically walking). I've also heard that BCAA's during the activity will help you keep your muscle.
Go by how you feel though. If you do fasted HIIT and feel like absolute shit afterwards and have trouble recovering from it might not be a good idea. Some people might have a unique capacity to handle it and consequently they advocate it, but it might not work for you
You should listen to yourself based on the results you've discovered through trial and error. After more than six years of training, you should have stumbled onto at least a few things that work for you and your body. Have you done any serious cardio or fat loss phases since you started training?
But as was said, the fact is you'll find differing opinions from credible sources on every topic, in the fitness world and outside of it. Some chefs make meatballs with just beef, some use beef and pork. Some lifters swear by the bench press for pec size, some say avoid it. Some people say don't use steroids if you're 6' tall and 180 pounds (ahem), some say YOLO. At the end of the day, you decide what to try and what not to and you decide what to keep and what to toss based on results.
But more on topic, fasted cardio was popular for so many years and was successfully used by many people (competitors and recreational lifters) that it'd be silly to flat-out say "it doesn't work." But it's just one application of one tool in the toolbox.
Is he arguing with himself? Did the method itself somehow change? Did he evolve his professional opinion based on the experiences he witnessed with clients? Sure seems like a head-scratcher, huh? It's almost like there really is no one single correct answer to apply to everyone.