He’s just being pedantic.
Technically ‘ls’ has kernel access because it depends on system calls in order to produce its output.
System calls are the mechanisms through which programs request services from the Linux kernel, allowing them to perform tasks like file management, process control, and device management. Any program that’s running on your machine has the access required to make syscalls and so you could say they have access to the kernel. They won’t have kernel-level privileges, so they can’t act as the kernel, but they do have access. Obviously the original user was referring to kernel anti-cheat modules which act as the kernel with all of the same privileges.
If a person stands to make a lot of money figuring out how to use a regular, non-anticheat kernel then they will do it. It would be a lot less difficult to do when the kernel code is open source.
For anti-cheats, it isn’t the case, as with Windows, where you can semi-trust that the kernel isn’t lying. If an anti-cheat runs and wants to see what DMA devices are connected it uses the kernel to do that and it trusts that the kernel isn’t lying. You could trivially modify the Linux kernel’s source code to not list a specific card when asked by a kernel module.