Clipping/Grabbing/Prolonging anchor ethics

In the beginning of the Climbing era and also mainly in Trad and Bouldering, you did not do the climb until you stood on the top. In Sport climbing and Lead comps we say that we have done routes just because we clip artificially placed anchors. In same rare cases, it is actually the crux to clip the anchor just because the bolter placed it wrong. In such cases, there is nothing wrong with prolonging the anchor with an extra quickdraw, especially for children. If you onsight and you reach the last hold but are unable to clip the anchor because of your reach, I think it could be considered as a valid ascent. Possibly, you should give it a lower grade if the FA added a grade just because clipping was the crux.