I understand the rule, we have this rule in place with a caveat. The rule protects us from a few common events, first being that where some developers just love to tinker with code outside the scope of their project. The second is simply a bad design where the results affected other code in unexpected ways.

There have been a few times were code was reverted and having the code merely commented out saved time, time spent cut/pasting from archive. Even with a good CMS keeping commented out code can serve another purpose, knowing what was when and why. That way we can avoid the "well back in year X we had a rule" because we have the code readily accessible.

For large blocks (subroutines/procedures/etc) it is not uncommon to move the whole to the end of the source.