RyanE,
A nice pair of well marked frogs, thanks for posting. Although there is a frog variation with the long central line of stitching unless I'm mistaken, the frog on the left appears to be a "mounted" pattern example that has had the retention strap removed. This was not at all an uncommon period practice. Sometimes the straps were cut away flush to the sides of the frog; other times the stitching was loosened or removed and the strap pulled out. The extended line of center stitching strengthened the back strap and helped hold the retention strap in place. Looks to be some missing thread on your left frog in that area and there is some horizontal puckering to the reverse showing where the strap was once affixed. If you examine the piece closely I think you will be able to see there was once a strap that has been removed.
The frog on the right is a "dismounted" pattern that was originally manufactured without a retention strap. Some of the dismounted patterns have a long central line of stitching while others are short like this piece. If "short stitched" the length of the center stitching may vary a bit but usually will not extend much above the bottom pouch. All three of these frog styles were made into 1945 with some slight manufacturing variations. My thoughts only ......