i.e. when triggering

./pants package example

is this operation repeated regardless of changes?

Yes. In fact all Pants operations that produce visible output files act this way. They basically can't assume the file already on the filesystem is up to date. IOW Pants does not 1st look at the output path, see if there is a file, checksum it and proceed from there. It does do something like that for all internal - invisible to you in normal circumstances - sandboxed operations, just not the final operations that materialize output to disk in your workspace.