Fresh install of Tumbleweed and I added the packman repository via yast.
Then ran these commands:
sudo zypper dup --from packman --allow-vendor-change
[sudo] password for root:
Loading repository data...
Reading installed packages...
Computing distribution upgrade...
Repository 'packman' not found by its alias, number, or URI.
Use 'zypper repos' to get the list of defined repositories.
Repository ‘packman’ not found by its alias, number, or URI. is flagged in red font.
You apparently misunderstand what this option does. This option applies to the single command invocation only. It does not “allow vendor change for the future” as you apparently believe. If you had installed the same packages from openSUSE, then you need this option to allow automatic replacement them with packages from Packman. If those packages were not installed, you just installed them from Packman and no --allow-vendor-change is necessary. So, either 4 or 5 was redundant.
Which is why it is impossible to answer your question “were they all installed with the command you provided” without seeing the actual output of this command - what zypper did.