Maybe your just lucky.
Going out on a limb here, but I think a bronze plate may actually outperform a soft steel plate. Should the plate be casehardened steel, THAT would be the most durable plate.
I can tell ya right now, if premature wear on a bronze lock was a issue, Jim Chambers would not make it. Period. ALL of his products are top notch.(IMHO) As for the bushing LC puts in the locks, If I remember correctly, it is a Oilite bronze allow bushing & it is "slick as @!*%?&" as LC would put it. I have had him put several in for me & they are fast & reliable. The York rifle I just finished has one in it (in a Deluxe Siler lock) and it is a great lock. How much faster does it make the lock ? I have no idea as I have no way of timing one. But I know the lock is plenty fast & reliable & produces a shower of sparks on each firing........... It would be slick if you would send the lock to Larry Pletcher and let him time it. He has records of hundreds of locks that he has timed. I wonder if the bushing really makes a difference??