Nothing is wrong with USBPorts.kext being put in 'Other'. In fact it is safer to use it in EFI/CLOVER/kexts/Other or EFI/OC/Kexts for Catalina and Big Sur.
For a start, no third-party kext should go in S/L/E for Catalina or later. Period. This is because of new kernel protection put in place by Apple.
This guide doesn't use USBPorts.kext. This guide was a slightly older method of configuration, relying on USBInjectAll.kext and and SSDT-UIAC.aml. In the
New Beginner's Guide we create and use USBPorts.kext.
The reason for the preference between the techniques is because USBPorts.kext contains no executable code. This is important for the latest macOS's. It is a method of altering the ACPI by loading, or injecting, the changes we need as a kext would. Because it has no executable it does not ring any alarm-bells for Catalina or Big Sur. It doesn't get blocked. If you put it in the EFI location macOS doesn't even get a sniff of it. Run the Terminal command 'kextstat' (when you get it all working) and you will see it is apparently not there.