zypper purge-kernels doesn't work as I expected...

In my /boot/ I got two kernels:
/boot/vmlinuz-5.3.18-55-default (current)

In my /etc/zypp/zypp.conf:
#multiversiondir = /etc/zypp/multiversion.d
multiversion.kernels = running

If I run “**zypper purge-kernels --details” **5.3.18-52 is not purged.

Reading installed packages...

Preparing to purge obsolete kernels...
Configuration: running
Running kernel release: 5.3.18-55-default
Running kernel arch: x86_64

Resolving package dependencies...
Nothing to do.

What am I missing?

I am running systemd-boot and not grub…I manually copy the kernel I want to boot to the EFI partition. Does "zypper purge-kernels"only work on grub?

Show output of

rpm -qa kernel\*