The kernel in the EFI partition is used as a tool to bootstrap hardware and memory for your proper kernel, which is chainloaded.
There is a simple reason for that: The Linux kernel can do anything a bootloader needs to do, especially for itself, so why not use it as one?
That said, in most setups there is another bootloader before that, which loads the kernel itself and the initramfs for that kernel. That can be for example systemd-boot, formerly known gummiboot, a minimal bootloader meant to (auto-)discover EFI compatible stuff it can load.