That explains the first prototype, but how on earth does it get through to production?
I believe the error was made and undetected on the first order for 100 boards or so. Being a shoe string start-up operation they probably could not afford to write it off and redesign, so they shipped their first products out along with shield boards that then had to be built to fit the non-standard spacing error design. After that they were reluctant to change the spacing because it would make all their present and 3rd party shield boards incompatible if they corrected it.
They do regret it I'm sure, but they probably did not dream that the arduino platform would reach so much popularity and fame and to this day still is something to keep them humble even after all their success.
There have been several retro fits for this 'problem' for people that really need to utilize standard .1" pin spacing, either with 'bent pin" shield connectors or utilizing 3rd party arduino compatible boards that add extra shield pin pads with standard spacing that one can use by just soldering in a new connector.
No matter how you cut it I can only see bad engineering practice. I know it was designed for artists, was it also designed by artists
Not artists but rather professors and grad students with probably little experience with production of other then prototyping projects. I think they hit on much too great an idea, open software coupled with open hardware, and a simple to use IDE that made micro-controller programming easier and cheaper then any other commercial company had offered at the time, to come down too hard on them for this start-up design snafu. There success points to the validity of their initial concept and that sure counts for something, no?