This issue is happening on both SLES 15 SP4 and openSUSE Leap 15.4, as well as
Tumbleweed.

Zypper is able to lock, and resolve the locks, for the `sles-release` package
and the `openSUSE-release` package (on their OS respectively), but the packages
can still be upgraded and removed.

`zypper ll --solvables` shows the lock
-------------------------------------------------------------------------
7  | openSUSE-release    | 3       | package | (any)      | 
    Keep installed : openSUSE-release-15.4-lp154.166.1.x86_64 (@System)
    Do not install : [2]
        openSUSE-release-15.4-lp154.166.1.x86_64 (repo-update)
        openSUSE-release-15.4-lp154.153.1.x86_64 (repo-oss)
-------------------------------------------------------------------------
but when saving the testcase, it doesn't containt said lock, and it's possible
to remove the package.

If the product itself is locked (shipped by the release package), it can't be
removed, as expected:
-------------------------------------------------------------------------
hobbes:~ (0)# zypper al product:Leap
Specified lock has been successfully added.
hobbes:~ (0)# zypper in -- -openSUSE-release
Problem: 1: conflicting requests
 Solution 1: Following actions will be done:
  remove lock to allow removal of product:Leap-15.4-1.x86_64
  remove lock to allow removal of product:Leap-15.4-1.x86_64
 Solution 2: do not ask to delete all solvables providing
openSUSE-release.x86_64 = 15.4-lp154.166.1
-------------------------------------------------------------------------

It seems the product lock is applied to the -release package but not the other
way around.