As long as they've had the OLM, but I think they have ramped up the weighting of the 'time' thing. (Perhaps so it matches the OM recommendation on low usage vehicles)
They have been known to 'tweak' the calcs it uses on different engines.
Yes, gassers are the same.
When they introduced it they got awards/praise in the engineering community for it.
I had read SAE papers about it, but was still a sceptic til I found one one of my vehicles that the 'mileage to recommended change' did change on MY vehicle when my usage of the vehicle changed.
Since each engine model has characteristics that are different, each one will have different weighting on the factors used in the monitor.
FWIW, fuel filter measures the restriction of the filter -- so resetting it does work like the oil life monitor. (at least the LML did)
OM also says fuel filter change should be OLM, but not to exceed 22,500 miles, and not to exceed 2 years.
L5P fuel filters don't seem to last that long, but on LML it was/is common to hit the 2year and/or 22,500 miles on one filter.