It is moderately important to NEVER interact with the contents of
folders such as your iPhoto Library or Time Machine backup except
through their respective programs (iPhoto or Time Machine, for
example). It confuses the programs and can result in remarkably
counter-intuitive and decidedly sub-optimal results.
The "bug" is that people are easily confused by the concept and user
interface for aliases. Apple could do better.
Another example of htis is burn folders. People copy files into burn
folders, then throw away the originals, not realizing that the "copy"
into the burn folder made aliases magically for the user. Ooops.