The original intent of Ruger was to create a Mag safety feature. The gun is not supposed to operate without a magazine in place. So try it... does your MKIII fire on a snap cap without the magazine in place?
Another "feature" of the mag safety was to restrict the drop free operation of a released magazine. They would drop about 3/8 to 1/2 inch so one could grasp the magazine and pull it free.
Some MKIII's do indeed drop they're magazines freely but some of the owners speculate this is more due to the "nub" on the magazines (that are held by the release mechanism) are worked down to a height where they no longer restrict the magazine movement, hence the mags drop without the intersticial holdup.
When you actually remove all the internals (related to the mag safety) and do a bushing swap the "nub" on the magazines no longer has a hold back device restricting it's ability to truly drop free.
MAke sense?