This is actually a horrible input for PatienceDiff, and the result is D (length of the edit script) is always exactly 1... a full replace.

The problem stems from PatienceDiff needing to locate a unique common point within each segment.  The generated input is segments of single characters, which wind up repeating and being not-unique anymore.  This is a corner case that PatienceDiff falls down on.  Consequently MyersDiff produces actual edits and PatienceDiff doesn't.

I'll try to come up with a better input.