No it is many more than that. From the percent I remember seeing and the number of engineers Google employs, more like 1500+? 7 is a high, difficult to get to level, average employees are not expected to pass 5, but Google is so large that's a lot of people.

Google stock grants vest over 4 years, so 8 years ago doesn't matter, but there is something to just tenure in that yearly refresh grants really add up, and used to be similar size to the first grant, so pay would really escalate over the first four years for many (most?) people.