Back in the day folks used to get upset that they're 150mm fork maybe only had 147mm of stanchion showing and Fox had an infographic somewhere that stated that something like 6mm of 'travel' could be taken up by the negative spring.
I find my Yari uses more of it's travel than my Fox 36 Grip used to, more often. Different forks will use their travel differently even with the same air pressure and # of tokens. If one is on a bike with higher bars/slacker HA it might use it's travel less as more weight is over the front wheel. Doesn't even need to be the fork itself. My riding buddy could never get full travel out of his 36 because his rear shock was too soft and at the same time he was a cautious rider so his weight was always off the back.