When you superheat or high alch an item and start mining rune essence BEFORE animation ends it will show you that you are standing still and rune essence is coming into your backpack.


In other words you mine essence without animation

Fun fact - after that invisible mining if you superheat another item (or alch) it will start mining animation but nothing happens (no ess mining)

You can cancel a lot of animations. Most of the cancellations are wanted to give people the opportunity to interact with the game quicker. An example for these interactions is the example you've given, alching an item while mining. I don't intend on changing this, because it would make the game unresponsive imo.