All Chassis Dynos have traction "features" called "creepage" and "slippage".

Creepage is "controlled slippage" and is usually very repeatable with a properly designed drive roller.
It's almost not measurable when transferring small amounts of power or in "neutral", unloaded conditions.
Under high HP levels on 2007ish sort of roadrace and street tires the usual level seems to generally be 3.25% to 3.75%.
Any much more than 3.75% and the tire / drive roller enters "slippage" and smoke often appears. (in other words, disregard any dyno info with smoke coming off the rear wheel)

Slippage is "uncontrolled creepage" at some rate and is greatly related to the amount of power that you are trying to transfer to the drive roller.

When you set a Tach Ratio on an EC997 dyne system, that ratio is optimally valid for the power range if it's done under full load, in the powerband range.
Calculating (automatically or manually) a Tach Ratio at zero load, like some dealership level dynos do, is incorrect, and produces incorrect data.

Famous '06 story of 3 R1's from the Pacific Northwest.

One stock with a pipe, one with a pipe, Factory Pro Velocity Stacks and tuned and the 3rd, a built engine, pipe and stacks and tuned to Best Power on an EC997 dyne system.
The stockest one and the "built one" were 15 True HP apart when measured properly, under load, with good traction, with the correct tach Ratio on an EC997 dyne system. Borne out in the real world - Bike 3 was much quicker than both the others.

The 3 bikes were brought to a local dealership's level dyno to see a bigger HP number.
The 3 bikes were only "4 djhp" apart in power according to the dyno operator.
The obviously strongest one, rather interestingly, hit the rev limiter about 8% earlier than the other 2.  That's interesting... Why would the rev limiter kick in earlier only on the dealership dyno? It didn't on the EC997 or the real world....

Hmmm...... If you added back in 8% hp to the poor showing that the obviously stronger (EC997 and road tested) bike, you ended back up to about the very same 15 hp difference between the slowest and the strongest bike as measured on the EC997 dyne systems with the patented slotted drive roller.

But - the dealership dyno operator only knew what his dealership level dyno told him and missed the clue that the smoke off the rear tire on only the #3 bike had. He was kinda curious as to why his dealership dyno showed that the rev limit kicked in at a bit over 12k, though -

Fooled by tire slippage on a knurled drive roller of the dealership level dyno and probably still thinks that tuning to an air/fuel ratio is correct??

How does Factory Pro avoid excessive error?

Factory Pro's EC997 Dyne Systems are all equipped with the patented Hi Traction / Low Tire wear  / Low Inertia wear Slotted Drive Roller system, invented by Factory Pro.
It's a required option on the new dyno price list.

Dealership level dynos use less expensive diamond knurling that slip under high hp.