It fits the profile for scaffolding. Horizontal pieces like this are used to strengthen or to guard. They do indeed have some pieces similar to this that are not broken down at all. I have seen these many times on the back of scaffolding wagons.

But I do agree with you that it does not seem like your typical scaffolding construction piece. Maybe an older piece but I guess unless someone comes forward that has used one of these before then we may never know what this item is.