The G2L comes with a metal bezel.
The P60L used by the G2L/6PL/Z2L etc etc has a thermal sensor that throttles back the power to the LED to prevent it from being damaged through over-heating.
The output of the P60L whilst the P60L is cool will be in the order of 80 lumens.
However, if used constant-on and/or such that the P60L heats up the output will reduce to a level at which it can be regulated without long-term damage to the LED.
The runtime chart shows this for a constant-on test. Note that the chart used a regular G2 as a host for the P60L so it didn't have the metal bezel.
The metal bezel improve the ability of the heat to 'escape' from the LED and be removed from the flashlight. As a result the output the P60L can regulate at will be higher compared to a Nitrolon bezel.
Because there is an active thermal sensor the in-use output will depend on plenty of variables including ambient temperature and humidity as well as air flow; whether you are holding the flashlight in your hand, in a gloved hand and the ability of your hand to 'wick' away the heat through the circulation of your blood (your body is a heat sink!); the state of charge of the batteries; the type of use (momentary use / constant-on use etc)
Some people may consider that SureFire is over-cautious regarding heat and that it can drive its LEDs harder but the P60L is an LED Lamp Assembly designed and built for plenty of use over a long period of term (used daily for 5-10 years).
Al