Utter nonsense. He's obviously confused. The only incompatibility anyone is going to encounter is between 1.3 (or 1.2, 2.0, etc.) and 3.1, while trying to run software that was designed for OCS/ECS machines on an AGA machine, and vice-versa. Each incarnation of KS introduced subtle incompatibilities that some software just didn't like. Or, introduction of faster CPUs that old software (often poorly coded, or, that was strictly tied to the timing of the old 68000 of the original A1000/A500/A2000) didn't like. It has nothing to do with the Gotek hardware.
I kind of find it funny how he is using FlashFloppy firmware in the menu selector mode -- that's not needed any more. Older firmware, like Cortex firmware (the first one adapted for use in Goteks and since abandoned due to people selling the developer's free software on pre-flashed Goteks on Ebay without his permission) relied upon that, but with an OLED and being able to directly navigate the USB stick for images with FlashFloppy and HxC firmwares, it is, in my opinion, an outdated mode of using the Gotek.
If you have any questions, don't hesitate to ask...we were all newbies at one time...welcome to the cult.