Why can you buffer casts while untargetable from Zhonyas/ stopwatch, and other untargetable sources?

Ever wonder how people manage to somehow slip away when under stopwatch or zhonyas from just barely dodging a spell? How they dash before you can target them?

Ive noticed that using an ability while in zhonya's queues this ability to be casted. This includes items, but does not include summoner spells.

Many scenarios (mostly 1v1) these people in zhonyas have distinct advantages because their abilities are guaranteed to come out frame 1, whereas you need to luckily time yours or need to wait until about frame 30 before your targeted ability hits.

So lets say I play .

I press Zhonyas after a big burst or something, and press R while zhonyad.

You literally cannot kill me here. My ult comes out frame one because of the buffer and I get to safety.

This can be used with a number of things. Dashes can dodge things people timed, queueing safety abilities and other things gives people who use the panic button an advantage, for absolutely no reason?

This is a panic button. It should be useful in certain scenarios but you shouldn't EVER have an advantage because of guaranteed frame 1 actions.