I looked it up and it seems like they're trying to make kickoffs function more like normal plays, which seems pretty sensible to me.

It looks like the onside kick rules are a victim of reworking kicks generally, so perhaps some fine tuning over time will help. The idea of only being allowed to do them in the 4th quarter and without the element of surprise is... somehow anticompetitive in my view. Imagine if you couldn't pass the ball unless you declared it to the other team before the play... it's just silly.