Yep, but the point is that - specifically and in this case only - some info is missing and Isobuster - exceptionally - is not the "right tool" to check (for some reasons)
Can you name the "other" tool?
Can you specify the exact (command line or GUI) options you used for running the test?
Or, can you create two (small, containing just the isolinux bootable file) images with makeiso and the other tool and upload them somewhere, providing a link?
Or, can you do a FC between the first sector of the "source" isolinux and the first sector of the IsoLinux actually "burned" by makeiso and the first sector of the Isolinux "burned" by the other unnamed tool?
Whilst (for other reasons) your tool iso_info is not reliable. (heck, you wrote it, and if something is wrong in the concept - not only in the implementation - of makeiso, likely the same error has been made in iso_info )
Theory of operation :
makeiso does not touch the bootinfotable (that shouldn't be touched as it is ALREADY compiled correctly in Isolinux, at least in the versions I tested at the time with Isobuster's Author) AND Isobuster thus lists the correct size (because it checks bootinfotable)
I mean, without knowing the details ALL of these are possible, as seen from here:
1) makeiso does corrupt the preexisting correct bootinfotable and THUS Isobuster lists NOT the correct size but defaults to 2 K
2) the other tool uses NOT the -boot-load-size 4 (or similar) and thus it doesn't touch the bootinfotable BUT ALSO does not set the size to 2K AND THUS Isobuster reads the "plain" size of the file
3) the other tool uses the -boot-load-size 4 (or similar) and anyway doesn't touch the bootinfotable AND the IsoBuster reads correctly the bootinfotable
4) the whatever version of Isolinux has a "wrong" bootinfotable and mkisofs correctly doesn't change it (but also doesn't verify it) ...
5) the other tool uses the -boot-load-size 4 (or similar) AND also the -boot-info-table (or similar) and thus overwrites (correctly) the bootinfotable AND the IsoBuster reads correctly the bootinfotable
The most probable is #1, you should know if you implemented any change to the bootinfotable, but also #4 (and the consequent #5 are possible).