Yes I agree I should have specified that.

I’ve come to the following hypothesis regarding hookless for road/tri:

Hookless w/ 28 mm tires gets you 90-98% of the performance (strictly talking aero and rolling resistance) of hooked w/ 23 or 25 mm tires depending on the wheels. Mfg’s are depending on the comfort aspect to the close the rest of gap and potentially even exceed it. We just haven’t found a way to objectively measure comfort or utilize an existing test/measurement (eg: lactate, hr drift, etc) and make it part of the overall equation.

I’m not sure if we will ever get the last part but time will tell.

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That's fair. I was OK on 23mm in coastal SoCal. Now I'm in the Sierra Nevada foothills. Expansion joints in every direction. 23mm is just brutal.

I agree that there's no significant speed advantage in Crr or Cd with hookless/wider/tubeless.

I'm still a huge believer in the latter two for reasons other than measurable speed. Rather I think their miniscule losses are worth the benefits. And I'm the guy with aero calf sleeves, etc.

My jury is out on hookless for road. It's in for gravel and MTB. No-brainers there. There is some nonsensical stuff written about the advantages. Enve's road hookless evangelical page is....puzzling....to me.

With a decent dataset from a accelerometer glued to the seat post and analysis of the power spectral density between two tires will tell us most of what we want to know in the sense of is tire A or B more comfortable. How that comfort turns into a performance benefit is more nebulous.

This also isn't true. You can drop the pressure some, and still have lower RR with the bigger tire (to a point). A wider/shorter contact patch has lower hysteresis losses than a narrower/longer patch.

We did capture the vibration data. We also asked the riders to give their subjective scores of comfort and we correlated with the vibration data.

As for "benefit", I guess we can use the philosophy of something is worth what someone is willing to pay for it. We asked the riders if when comparing the pressure before and after the 5bar breakpoint if they would "pay" say 4watts for that, the answer was no.....2....not even....

I think this is a strawman logical fallacy. Or you are not seeing the forest through the trees. It looks like you are setting up casing tension as the ultimate measure. But it is truly irrelevant. Those experts are finding the fastest system, and they do not care about casing tension. They are using their testing protocols to determine the fastest combination of wheel, tire, tire width, and tire pressure for their riders. The end result is that many of them are on wider tires, some as wide as 28mm. And they are on lower pressure too, but not as low as the 5 bar hookless max.
I'm not sure I need anyone to quantify comfort. Though, marcag did make an effort to capture that from his riders.

My personal experience is that I did a fondo event on a demo bike. I had no agenda and no plan to buy a new bike - I loved my 7 year old bike. I did a test ride on chipseal pavement and was blown away by how much smoother it was. My friend at the event had the exact same reaction on his demo bike. It was kinda unbelievable how much better the wider tubeless felt. Both of us were running 25mm on our personal bikes, but at 80 PSI. We talked to several of the pros in the event about bike comfort, wide tires, pressure, etc. By the end of the event, I decided to buy one of those bikes, almost on the spot. It is radically more comfortable than my former bike.

It is my road bike, and I do not ride it for maximum speed, so that was not part of my decision. But the consensus opinion from reading here, by other experts, and a few former pros, is that you do not give up much speed, if any, on wide tires at 60-ish PSI. And the comfort factor is a huge bonus.

I think this may be an inadvertent case of selection bias. I don't know many people riding 23mm, 25mm seems to be the standard for narrow tires. (on a tangent the ideal road racing tire on modern rims is probably 28-30, the draft in a race changes a lot of the numbers from tt/tri world)

Regardless, for the switching anecdote I can think of three big groups - 1) Got new wheels and the optimal (or at least very close to optimal) tire size is ~28 because of the rim design. No reason to switch to 23's. 2) Kept old wheels and didn't change tire size, not part of the given sample. 3) Kept old wheels and moved to 28's. I don't doubt that the preponderance of people in this specific group also kept them, but they were either speed or comfort driven - comfort makes sense, but if speed driven surely they saw some benefit to the switch.

The point I'm getting at is that someone wouldn't switch to 28's without a reason, and that reason would need to be found false for them to switch back. Not just a little false, but false enough for them to admit to themselves and their riding buddies that they got it wrong.

Disregarding hookless for the moment. Have you found that the lowest achievable losses on a 28mm tire is better 25 or 23mm (assuming same wheel).