The only patching that seems to be done to the ISO created by it is that a string containing the start of the XSF header is written to the start of the new ISO image. It's actually written incorrectly however, since the XSF header should be written as:
0x0, 0x5853461A ("XSF")
0x4, 0x400 (XSF sector size)
0x8, 64-bit uint value for the total size of the ISO image, minus the value at 0x4.
Froggy's app seems to only write a static value of 0x277C00 for the ISO image size, which won't stop the ISO from working as a GOD, since converting to a GOD container discards this sector of the ISO image anyway, but its not correct for the XSF standard.
Having said that, Froggy's GUI does a good job at making extract-iso easier to use for people that don't like command line tools, so it does it's job quite well. But I agree, credit should be given to the original authors of extract-iso since that's what's doing the hard work here.