Hitting Pure Flattened Movement?

It's possible. A random with an even distribution is less predictable than a skewed random, but it's only a hunch that curve flattening resembles the former.

But while knowing where they won't be is something, and could increase your hit rate, it's really quite far from knowing where they will be. You could know where they won't be 100% of the time and never hit them. :-) And of course there is a correlation in random movement between where they have moved and where they will move, since they are determined by the same algorithm. Isn't it more useful to know where they will be vs where they won't be?

To know where a flattener will be, you'd have to figure out quite a lot about their stats to be able to shoot at the least visited reachable point with any accuracy. And that truly is the holy grail of Anti-Surfer guns, since you could also destroy a normal surfing system if you knew that much (ie, not just a flattener). When surfing first came along (~2005), a lot of folks thought this would happen almost immediately, but so far they are still wrong.

Knowing where they won't be increases your average hitrate over time, by limiting the places they could be. Imagine a targeting system which fires outside of their MEA vs one that always fires in the MEA.

Oh for sure. My most sophisticated attempts at fancy Anti-Surfer guns were along these lines - assume they will go to the safest reachable point on all of the waves in the air at fire time, using precise prediction to figure out reachable points, then restrict my choice of firing angles to the range of remaining reachable points.

What I really want is a mask to apply to the whole range of firing angles, deduced from the probability of all possible enemy movements as they surf the waves in the air. I tried a very (very!) crude version of this once in Dookious.