My apologies for ignoring you, sir; it's tougher to go in sixteen directions at once than I first thought.

1921 San Francisco coins demonstrate these "horns" frequently. I've seen lesser versions of them on other Morgan issues, but 1921-S has taken it to a whole new level. I'm thinking it's a combination of lackadasical die alignment combined with pushing dies to their limit in order to produce enough coins.
Your first example is as extreme as I've ever seen it, and on the opposite side of the obverse die than normally found. It's usually at the bottom, most obviously the date. The obverse strike is
really soft at the periphery - look at the dots either side of "E PLURIBUS" - and the stars look "drawn" to the rim, indicating a very worn die. Yet, the center of the die is strongly-struck - the intersection of hair and ear is the first place one sees a weak strike on the obverse, and this coin is sharply-detailed there.
Makes me wonder if these dies were more than normally convex, and if that was deliberate, knowing how many coins they would have to strike.