Is there a writeup on why they choose to destroy the history?
* Contributors without github accounts * Moving away from github (when needed) * No vendor lock-in for github stuff.
I personally think, this is a good idea - a lot of work, but may be worth it in the long run.
edit: rereading, I guess the implication is that there's tooling built on top of Github outside of Git, so Git history is indeed not meant to be contain some things.