Not sure I'd trust so called "knowledge" from a Vintage Bike guy. The fact is, low power vintage bikes have such low HP that they will rarely test a modern motorcycle chain. Chains today are another world from the bad old days of Vintage bikes ... and good riddance!

If he was running Hyabusa's, top speed testing, that would be more credible. How many Race teams use Iris? DID chains are used by several TOP MotoGP and WSB teams and are the biggest seller in USA ... by far.
Now, why is that?

The Japanese have built a whole industry around manufacturing chain ... and they compete fiercely with one another. At the moment ... and for at least 15 years, DID have dominated the motorcycle side of this industry.

In USA we do see some activity from RK chain and EK. EK is a lesser known Japanese chain manufacturer, RK have been around decades. You also have Tsubaki and Regina struggling to hang on.

Most Japanese OEM's now use a DID chain from the factory. The DID chains put on bikes at the factory are NOT DID's best chains ... they are simply mid level O ring chains for the most part. It's fact that X ring chains give longer service life and rarely ever need adjustment. With 250K miles of experience with these ... I have empirical evidence.

I've never heard of Iris ... I would want to know which OEM's use Iris chains on their bikes from the factory?

When Triumph was reborn in the UK in around 1993, they started out using
Regina chains. Somewhere around late 1990's they had a run of serious failures in the form of multiple warranty claims.
Many of these Japanese made Regina chains were failing within 5000 miles or less. Obvious flaw.

Lots of British riders blamed Triumph for this and tried to say the whole bike was crap ... (total BS of course) Triumph reacted quickly and made things right.

Triumph discontinued use of Regina and have gone with DID chain ever since.
I've owned 3 Triumphs ... the first a 1995 885 Tiger. It's Regina chain needed replacement at around 6K miles. My next Tiger (1999) had a DID. When I replaced its chain (I was in UK at the time) all I could find quickly was an EK chain.

That EK chain did OK, I put 20K miles on it and it still had life left in it. Not bad.
My last Tiger (2007) was new generation 1050. Of course it uses a big 530
DID O ring chain. It lasted well, was still OK at 22K miles.

But my DID chain experience goes back to the 90's and adds up to about
250K miles of use, primarily using DID 525 VM2 X ring chains (the VM2 was top of the line DID chain at the time). These VM2 X ring chains are no longer made but the ZVM X ring is it's replacement and hopefully is as good. I've got one on my DR650 now.

I got 25K miles on average on my VM2 525 sized DID chains. Over 100K riding my Vstrom 1000, more miles on TDM 850, Triumphs and several DR650's. Current DR650 is up over 60k miles.