Right. If you check the info, what Science ships actually get is:
Beam: Target Shields I, Beam: Target Weapons I, etc.
Tactical officers can get Beam: Target Shields II, Beam: Target Weapons II, etc, as normal Lieutenant-grade skills.
Hypothetically, the Science ship versions are 'Ensign'-grade versions of those Tac officer powers. Except ensign-grade versions of the Beam: Target powers don't actually exist as trainable BO skills.
This means the Tactical officer Lieutenant skills are better than the Science ship equivs. They're grade II, not grade I. But of course Science ships get theirs for free.
Not just the grade differences.. they work differently as well.
From what I have seen, the powers given by the BO skills will give a guaranteed hit to the subsystem in question, where the sci ship innate ability gives a CHANCE to hit, and if it misses, will debuff that system for a short time.