Interesting, what are the biggest differences between pro rider fork setup and "15s racer"?
Or are requirements that much personal, that one pro has more and other less damping compared to Ohlins factory recommended settings for for example FGRT201 forks?
I had chance to make 3 laps on IDM rider gen4 with FGRT201 forks and that had much less compression damping making front dive quickly.
First & most obvious the physics working against a bike chassis at or near the lap record are exponentially higher than the guy riding around at 15 seconds off the lap record. The bike near the lap record is moving around, compressing the suspension, flexing the frame and drifting all the time and that all has to be controlled predictably. To get a rider to that level takes a lot more technically correct suspension set-up focused to those needs. Those riders, as awesome and skilled as they are, do not get to that level on their own. It's a team effort and a lot of it.
If you take a newbie ham-fisted rider and just arbitrarily remove most of the oil from his fork tubes like you would end up doing for a pro racer then you are risking the event of bottoming out which is catastrophic. When a rider actually touches the inner stanchion to the fork cap while in a turn it almost always results in exceeding the tires grip and a front end wash. That is why we have higher oil levels and hydraulic stops for street bikes and the like. It's a safeguard.
When you work with faster riders you can read their data and know how much fork travel they are actually using and where on the track that is happening and you can tune the suspension for it. This always includes custom oil level and spring rates which varies even more when you have gas kits where you have additional pressure inside the forks to factor in. Gas kits are even more reliant on the riders specific style and requirements. Additionally we almost always use a higher spec valving to compensate for those additional forces on the bike regardless of whether it is conventional or gas kits. There is way more to it, but to try to explain it in detail would take a novel and way more time than I can spend here talking about it.
In my experience there is a line around 8 seconds off the lap record where things start to happen and custom attention is needed for suspension bits. That's where the FGRT201 forks for example "as delivered" aren't going to be quite up to the task and need some help to get them to that next level. That being said most riders are not at 8 seconds or less off the lap record. Most trackday guys are easily 20+ seconds off the lap record at any major circuit so those forks work wonders for both the physical requirements of making their bike handle properly as well as their own mental confidence. They are riding faster with less drama so it is money well spent. If they want to go faster and are capable of it there are better options with gas or spring charged cartridge kits to get them there, but like always speed is a question of money. How fast do you want to go equals how much do you want to spend?
The bottom line is riders at or near the track record are getting a focused level of support where intimate knowledge of the trade is applied in a manner that would be mostly if not completely irrelevant for riders 15 seconds off that pace. In my years I have ridden one World Level Unobtanium Superbike and several AMA Level racebikes and all of them were basically un-rideable at 20 seconds off the lap record. One AMA Factory 600SS bike in particular felt like I was riding on wooden shocks on a warm up lap and the bike would protest the input into every turn, but get it down to 10 seconds off the lap record and it started to feel almost normal, 7 seconds off the lap record even better and almost instinctual entering every turn. Now I couldn't go any faster than that because I am just not a good enough rider to do it so I don't know how much better it was going to get, but there was no denying that the faster I went the better the bike handled which is the exact opposite for a bone stock bike off the showroom floor. From a streetbike having to safely carry a rider & passenger to Hooters on Bike Night to a racebike designed to carry a solo rider to a championship at the lap record. It's all in how the set-up knowledge is applied and it is very specific for the task.