I'll admit that I was surprised by how solvable this puzzle was, despite not having an obvious starting point in the form of two adjacent copies of a single letter. I thought it'd be insanely tedious trial and error in typical PuzzlePicnic form, but I broke in and solved it without straining myself.
I'd consider making some of these myself were it possible to customize the characters beyond "A through some other letter". (As an example, Nikoli once published one where you had to partition the grid into blocks containing permutations of JAPAN, NIPPON, and ZIPANGU.)
I'll admit that I was surprised by how solvable this puzzle was, despite not having an obvious starting point in the form of two adjacent copies of a single letter. I thought it'd be insanely tedious trial and error in typical PuzzlePicnic form, but I broke in and solved it without straining myself.
I had the exact same experience. I'd done the other 3 on my lunch break the day they first appeared, and when I got to this one I looked at it for a few seconds and dismissed it as not a lunch break puzzle.