One naive way to do this would be to create ligature pairs for difficult pairs (mi, lm, etc). But instead, they seem to be selecting character alternates that fill the fixed width differently based on their surroundings.
In practice this is unusable. Because the width of the letters now depends on the succeeding character, the text jumps as you write it. Super annoying.
Cool for reading. Awful for writing.
[append] Oh, I do see some jumping when I type "optimized". Honestly, it doesn't seem very jarring to me; the jumping is always right where the edit point is so the added or removed letter causes a much bigger jump.