Is this sort of mix necessary for them, or just a traditional thing like putting Neos on mounds of sphagnum?
Let me preface this by saying that jokerpass is an amazing resource and much more knowledgeable on Jensoa Cymidiums than myself by far, but this is one topic where we generally disagree on the answer to your question. I am glad to see that they are at least coming around a bit on the topic, but I still disagree. Really, I wouldn't even care to mention it, but I don't want people to be discouraged from trying these Cymbs thinking they have to find obscure (and often expensive) potting media constituents.
I spent my early orchid growing years avoiding Phrags because certain folks made it sound like they were so exacting in their requirements that I might never be successful. Now it's my favorite genus and I consider it to be the easiest to grow and bloom of my orchids. I avoided Cymbidiums for almost all my orchid growing years because certain folks made it sound like they were tough to flower in my region. None of it was true, and I wish I had discovered these genera earlier in my obsession, but I let others convince me that they weren't a good fit. That's what I want to avoid contributing to here.
Now full disclaimer: I live on the east coast USA in a 7B region, a climate which is similar enough to what some populations of C. goeringii experience in their native habitat that they are actually considered cold hardy here and some people do grow them outside year round! So, that definitely influences my experience with this species, and that experience may not translate for others who don't grow in a similar climate.
All that is to say absolutely and unequivocally, my opinion is that no, this sort of mix is not necessary for them. Good news! I only have a few varieties, though, nothing special, expensive or fancy so it's definitely possible that the expensive and super rare (in the USA) types are more finicky and demanding.
I grow my C. goeringii and other Jensoa Cymbidiums in my standard orchid mix which is some random combination of whatever I happen to have on hand at the time. That generally means a mixture of orchiata, large grade perlite, rockwool, leca, volcanic rock, expanded slate, etc and I tend to go a bit heavy on the mineral based, inorganic stuff. Cymbidium goeringii, its hybrids, and its relatives love it. keep in mind what I said about people growing Cymbidium goeringii in their gardens around here. Those plants are growing and blooming just fine in dirt (which tends to be a thin layer of topsoil on top of heavy red clay) with a layer of mulch/leaves on top. They don't seem that picky about media.
Anyway, in my opinion, the secrets to good growth and heavy blooming is hot, wet, and bright summers with heavy feeding and then cool/cold, dry winters. Maybe the special mix makes a difference, maybe it doesn't, but I don't use anything that fancy and my plants aren't exactly huge but they always seem to have much more than 1 spike per season. I think my smallest little plant just produced 6 or 7 spikes back in January.