Yes. You are correct on your guess. The saves for the PAL copy will not work for the NTSC version. This has been true for every console to date with very few exceptions.
Note that I didn't say that all games were like this as there were a few that were cross-region compatible but not many. It is safer to assume that a PAL save will not work on a NTSC game copy due to the differences that the actual save file format may have.
Bookmarks