Well, actually it was introduced after Chrome switched to this same model. So it looked like Chrome is advancing faster because they released a new major versio

Well, actually it was introduced after Chrome switched to this same model. So it looked like Chrome is advancing faster because they released a new major version every few weeks and it got more press. I suppose that's why they really switched. If it would be just a matter of the management system you'd better adapt the system instead of version numbers. Anyway, after so many "major" releases the press has died down. So what we have now is version numbers that are quite meaningless because you can't pin major changes in the architecure to version numbers anymore.