"But head mounted displays made by Google haven't been available for years." Sure, but this makes your point into a circular argument. In your first comment y

"But head mounted displays made by Google haven't been available for years." Sure, but this makes your point into a circular argument. In your first comment you indicate that the fact that these glasses have been spotted shows that Google is able to make progress. Now you're saying that the reason that progress has probably been made on the glasses is because they're made by Google. I do agree with you that they are probably pouring a lot more resources into this than others have. I just don't think that sighting of the glasses in public indicate anything about what progress they've made.