I'm on openSUSE Leap build-ID 685.2 with libzypp-17.23.6-lp152.1.1.x86_64 atm.

Any "zypper dup" or "zypper up" command which involves updating kernel packages
results in the removal of all "kernel-default-devel", "kernel-devel", and
"kernel-source" packages. I tracked it down to the new "purge-kernels" command
of zypper, which on my system currently shows this:

# zypper purge-kernels -D
Reading installed packages...

Preparing to purge obsolete kernels...
Configuration: latest,latest-1,running,oldest
Running kernel release: 5.7.3-1.g44c4af0-default
Running kernel arch: x86_64

Resolving package dependencies...

The following 6 packages are going to be REMOVED:
  kernel-default-devel-5.3.18-lp152.19.2
kernel-default-devel-5.7.3-1.1.g44c4af0
  kernel-devel-5.3.18-lp152.19.2 kernel-devel-5.7.3-1.1.g44c4af0
  kernel-source-5.3.18-lp152.19.2 kernel-source-5.7.3-1.1.g44c4af0

6 packages to remove.
After the operation, 1.7 GiB will be freed.
Continue? [y/n/v/...? shows all options] (y): n

I deliberately chose to have the devel and source packages installed, so why is
installing updates removing these packages? This looks wrong to me!