You should be able to get that maximum (70-72fps) with 4x FSAA in Half-Life. People who report higher readings are liars, dirty rotten liars🙂. I like the limitation, helps with keeping people's multiplayer performance up to speed, plus it's not like you can discern a difference between 70 and 100fps.
Grr, this always bothers me. People, the game/engine is HALF-LIFE, not Counter-Strike, get it right😉.