Ignition cylinder
The manual and automatic cylinders are not interchangeable. The automatic interlocks with the PRNDL selector. Instead of the push button, you need to be in "Park" in order to turn back the cyllinder and withdraw the key. Since the manual doesn't have a PRNDL selector, we have the push button to make sure we really want to take the key out. This is a key safety feature.
In old school cars, there were many fatal accidents where people accidentailly knocked the key off and out while the car was moving. There was also a swath of "ignition switch deatths" a little while back: https://www.aboutlawsuits.com/saturn-vue-recall-69565/ ...So, you get the putch button to make sure you really want to take the key out and to add extra insurance that people with heavy key chains don't have their keys fall out. (If I remember correctly, some of these accidents were caused by people having a bunch of junk on their key chain which had enough weight to turn the ignition off and pull the key out when they hit a bump.)






