Doesn't that also indicate that there is a problem somewhere that the workflow-cps plugin which provides the parallel step and the load step is no longer documented in the pipeline steps files generated for jenkins.io?
Other "internal" steps (like stash, sleep, sh, bat, and node) are documented in workflow-basic-steps and workflow-durable-task-step.
It certainly seems like an error that the site deploy does not remove deleted files (as described in WEBSITE-630).
It also seems like an error that the workflow-cps plugin provides two crucial steps (load and parallel) which are not documented on the generated site. I assume they were generated previously but are no longer generated, or the generator is failing to generate them but instead of writing the file with the No DataBoundConstructor error, it removes the generated file.
Since the git plugin generated page is the current "winner" of most voted "Not helpful", I'll need to learn how those pages are generated in order to improve the documentation of the git step. More to do...