I never heard of a steel change in the BMF/LMF lineup. I've owned an original first year BMF back in 1987, and owned subsequent years BMF's and could tell no difference whatsoever in the steel type or edge holding ability.
The designs changed a little over the years, with blades lengthening, sawback serrations lengthening, and even dropping the sawback serrations on some models.
I'm not doubting it did undergo a change in steel, but I have not seen evidence to support that. It might take a former/current Gerber employee/manager to verify.
Welcome to the forums billraz! Do you have direct info on this steel change? Also, many will argue that the 425 Modified and the 420 series steels are not as optimal as 440A.