Kick 1.3 was really a minimal recompile of 1.2, with the romboot.library added to allow booting from HD - this was the really new part that arrived in 1.3. Everything is just 1.2 as it came, most bugs included.
I could not disagree more. I was an actual beta tester for OS 1.3 and it was much more than 1.2 with the HD boot fix. There were quite a lot of bugs fixed in 1.3 and some real improvements as well.
It has been a long time since I thought about this but the biggest change came in the file system. It was more robust, it handled minor errors way better than 1.2, disk doctor was finally killed off, and it was more stable.
I used to post my bug reports on BIX at the time. Good memories!
-P