Iirc, at least one design used a counter + ROM table with brightness values. And ROM table of bigger size (1k+ entries or so?) than one might expect. All this because a pseudo-random generator wouldn't produce nice enough effect. And b) counter + ROM asic still cheaper to manufacture in volume than a uC (probably not true anymore?).

But I'd be interested what OTP tech uC from the article uses. Mask programmed? Fuse-based? Flash? (and if so: erasable?). Something else?