The following information is publicly available (also on posted on internet slides from Sony-PSP shows). To save you some time and searching (not that most of you would have put the effort into finding that information) I will recap:
When writing PSP software the developers can chose to access files through directory list (that is the usual file name/location) which is much slower, or through using LBA access.
When using LBA the file access is tied with the UMD/ISO structure (file position on the image/disk) this is why modifying any ISO will result different LBAs then desired.
This of course besides faster in-game access to files LBA access provides increased security, since if anyone succeeds in copying the files of the disk image will fail miserably when attempting to execute them.
I hope the above made you smarter and wiser. :boohoo: