I'd love to be that good. I'm not. The level of preception and knowledge that is required for this to happen are beyond my abilities as a human being.
In my experiences in dealling with real threats and effective attacks (real threats), I simply cannot do this and it requires me to interupt and change the situation by dealing with the core of the threat.
If I could be behind them before they could attack, then I would not need to ever carry weapons and could go into combat empty handed. A nice thing to be able to do.
Hi. I'm glad you said that Kevin. For that statement leads to the core of irimi, the secret of irimi.
In practice I prefer, in fact by far prefer, facing a sword (bokken) empty handed. This is where you learn the core of irimi.
This is where you learn irimi for you definitely don't stay on line yet you do have to enter to join, to take control, to be with. Of course the practice would be from a shomen attack.
From a yokomen attack you would learn the core of tai sabaki used for turning inside too.
But back to the point. Empty handed against shomen doing irimi done expertly leaves you standing behind or at worst part next to and part behind. It's a scary discipline for to get it right the off line is very close to the actual line, therefore not as much as 45 degrees, more like 10 or 20.
It feels very 'sacrificial' until you are used to it at which point it feels the safest thing to do. Hence the need for calm mind and the complete awareness of center line.
Of course in real situations the first thought is to interrupt or parry and move etc. but hence my view that beyond that, you can learn to move in such a way that it becomes more effective than interfering and thus my view of aiki motion.
Both work, both disciplines.