Here is how it works!
Under normal conditions.
When you launch Logic - autosave files are generated once a minute and stored in the autosave folder. If you quit logic normally - those autosave files are removed.
If logic exits abnormally ( then when logic launches again it finds files in the autosave folder) because only on a normal exit are they removed. If it finds those files - you are prompted to use them or the last saved file to load into logic.
After you pick one of the two options and you then again close logic normally at some point later in time - those files are removed.
I have verified this.