That's a false assumption.
Lots of objects get changed outside of the source. Especially printer
files. Hey, let's run a CHGPRTF to change... A good change management
system will flag you when something was changed outside of the change
We were running into issues where we would promote a new printer file
change, miss the CHGPRTF issues, and users got upset.
Other possible issues: CHGOBJOWN, CHGAUT, etc.