Try using Attribute Adjust Vector SOP to handle this. Depending on how your source object is aligned, you'd want to adjust either the N attribute or the up attribute.
If you did want to randomize orientation fully, you'd want to write to `orient`, not `orientation`.
MOPs Randomize [github.com] is also a pretty user-friendly way of randomizing orientations, among other things. It'll work on template points as well as existing packed primitives.