who is Ackley and how did he improve everything?

P.O. Ackley was a cartridge designer among many other things. He took many standard cases and sharpened the shoulder angle and moved it forward there by increasing case capacity. He has written many books that I'm sure you would enjoy reading. Among his works is one of my favorites
"Handbook for Shooters and Reloaders"

I'm sure others will elaborate on this in much better detail that I, but in a nutshell an "Improved" case is one that the shoulder is made steeper, which in turn makes the capacity of the case larger, so it holds more powder.

P.O. Ackley was one of the first people to do this with a bunch of different cartridges, which is why you hear his name mentioned so much.

Now, if you are just joking I have to say that's a good quote! Similar to "How come nobody can ever hit that dime?!"

Fair question.
What is said to this point I believe to be true.
What also seems to be true is that every cartridge that is blown out (improved) seems to get the AI prefex.
To me this handle is over used. P.O. did a lot . No question, but others before him and his contemporaries were puffing out cartridges to get greater volume; Newton and both Fred and Frank Barnes just for starters. Me thinks it's becoming one of those expressions used by the in crowd. roger

Roger's conclusion regarding the overuse of the AI prefix is particularly applicable when one sees the term applied to newer cartridges that didn't even exist during Parker's lifetime.

Russ