keep in mind how priority & trades work, fundamentally
if at any point the yellow hurtbox's come in contact with someone elses red hitbox, you will take damage
if, at the same frame, your red hitbox hits their yellow hurtbox, they will ALSO take damage, and you get a trade
however if your red hitbox hits their yellow hurtbox, without your yellow hurtbox being touched by their red hitbox, you will hit them.
this could happen from the tip, or from above, or from below. aerial moves don't -beat- other moves, they operate under these conditions
ground moves, however, can -beat- moves, which is why you cannot time a jab to beat a forward smash
ground vs. air moves operate in the same way air to air moves operate