In practice, any ability to jump away at all means any competent CMDR can avoid being followed by anyone.
[...]This is fast enough to counter someone who knows exactly what system was jumped to the instant the wake appears (such as in cases where there are only one or two convenient escape destinations, the defender isn't taking measures to conceal the final destination, and the attacker selects the same destination system immediately, if they don't already have it plotted), well before there has been time to scan it.
^This. Some pirates even advocate omitting wake scanner and instead just trying to pre-emptively eyeball the system based on target heading since this is faster and frees a utility slot. But it can be countered by target using false direction until last few moments of high wake FSD charge, then boost in other direction.
And as Morbad says, even this really isn't fast enough.
So I just carry a wake scanner as a lazy way to track commanders who don't know any better.
Also, if in a long jump range ship, having a destination selected that is likely beyond the single jump reach of an attacker is guaranteed escape. I had a commander down to 30% hull use this tactic on me, was a great decision on his/her part since I had the wake scanned and ready to follow in about 6 seconds. Of course, by the time I used gal map to pursue via 2 jumps, said cmdr was long gone. We had a nice (literally, not sarcasm) little DM convo after that.