I guess Colt installed the hardened bushings so they didn't have to bother with ensuring the firing pins would line up with the firing pin holes.
I have been trying to keep this discussion on a respectful level without making snide remarks.
Allow me to quote from Jerry Kuhnhausen (who has probably forgotten more than I will ever know about Colts) in his Colt Single Action Revolvers Shop Manual. He refers to the part in question as the Recoil Plate.
"S.A.A. Recoil Plate notes:
1. Although S.A.A. recoil plates were made in .001 increment oversizes, most are in the range illustrated above*.
2. Early recoil plates were made from early and transitional carbon steels.
3. Intermediate through late recoil plates were made from 1060~1080 steels to increase durability and resistance
from firing pin wear.
4. Intermediate~late S.A.A. recoil plate hardness is approx. RC50.
5. Adjust replacement plate thickness to frame recess depth before installation and final crimping."
* the measurements illustrated are .085-.095. The red highlighting is my own.
All primers back out of the primer pocket as a round is fired. Then as the round slams back against the frame in recoil the primer is reseated.
Here is a photo of where the firing pin protrudes through the frame of my 1880s era Merwin Hulbert Pocket Army 2nd Model. Notice there is no bushing protecting the soft metal of the frame. Notice the cratering around the hole caused by primers backing out as they fire and slamming into the frame. Notice the peening of the frame near the top of the firing pin. This is what Bob Wright observed when he saw cratering.
Here is the frame of a S&W New Model #3 made in 1882. Notice it has a hardened bushing surrounding the firing pin. Notice there is no peening or cratering.
Smith and Wesson and Colt pressed in bushings like this for over 100 years. Do you really think they would have continued doing so if it was unnecessary? Nobody pinched pennies like Daniel Wesson did.
It's what I have been saying all along. Time is money. Uberti makes some very nice revolvers. But they take some shortcuts to save money.