It's a special case of automated client software updates, though.
Most of us are probably more familiar with systems like Firefox, Chrome, or Sparkle. The App Store mechanism is more complicated, and interesting.
The third party data (version string) that you don't want to trust is, in this case, very carefully screened by Apple as part of the submission process. It is trustworthy by the time it lands at the App Store -- but since Apple owns the whole workflow, they have much better options.
Most of us are probably more familiar with systems like Firefox, Chrome, or Sparkle. The App Store mechanism is more complicated, and interesting.
The third party data (version string) that you don't want to trust is, in this case, very carefully screened by Apple as part of the submission process. It is trustworthy by the time it lands at the App Store -- but since Apple owns the whole workflow, they have much better options.