One online dictionary has the following meanings for "true":
8. Exactly conforming to a rule, standard, or pattern: trying to sing trueThe Longman English Dictionary Online:
9. Accurately shaped or fitted: a true wheel.
10. Accurately placed,
delivered, or thrown.
11 straight/level[not before noun] technical fitted, placed, or formed in a way that is perfectly flat, straight, correct etc:
If the door's not true, it won't close properly.
12 somebody's aim is trueif your aim is true, you hit the thing that you were throwing or shooting at
5 a : that is fitted or formed or that functions accurately b : conformable to a standard or pattern : accurateNot only does my action bring about a result that is intended, but the intended result is what is appropriate or in accordance with a standard or rule. So in the case of firing an arrow at a target -- my aim is true when it, coupled with my technique of drawing the bow and releasing it, leads to the arrow hitting the target.
While we may understand truth as it is defined with respect to products of art, truth as it is defined with respect to morality may be more difficult. But is it so hard for people to understand and re-present Aquinas's account of practical truth correctly? Perhaps it is the interplay between appetite and reason that trips people up.