my question is, what was the porpouse of the concrete pump truck? was it so the concrete fell down on the heating system, to reduce it from moving sideways, as if you poured right out of the truck?
That's correct. With the pex pipe and styrofoam you can't lay boards across for wheelbarrows. The piping is only held down by grooves cut in the foam and the little plastic clips over it stuck into the foam. It certainly could be done with extensions on the truck, but it would require more attention and you know how today's workforce is! For me it was worth knowing I had one less thing to be concerned about. :D