The "no touching" thing is just a "cool visual factor" that sometimes happens when someone hits with aCoC, sometimes doesn't, just like splitting the sky.
It's not like they split it with the shockwaves of their attacks or the sky would keep splitting with every single clash during Luffy vs Kaido in different angles. It didn't even split during the final clash with a giant island-sized punch and that attack was certainly stronger and carried better haki than the attack that had previously split the skies.
So no, it's not a matter of "having stronger aCoC if they can split it" or if "they don't touch" (Luffy and Kaido touched plenty of times while using aCoC), it's a matter of Oda feeling like making it a moment or not.