A unit doesnt have a "wounds characteristic", only models do.
DATASHEETS
4. PROFILES
These contain the following characteristics that tell you how mighty the models in the unit are.
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Wounds (W): Wounds show how much damage a model can sustain before it succumbs to its injuries.
You cannot select a unit with 10 wounds, only a model with 10 wounds. A unit who has one model with 10 wounds in it, is a unit.
If we go by strict
RAW, the beam of unreality doesnt work, because a unit doesnt have a "wounds characteristic".