It looks like those statistics have summer months included. That changes things from "60 hour work weeks when school is in session" to "60 hour work weeks amortized over a year".
In addition that study notes that teachers are more likely to work a second job, something a Google engineer wouldn't need to do to make a decent wage.
Many jobs in our society enable others to do efficient work. From the bus drivers that get Google employees to work to the teachers that work 60 hour days educating future doctors and lawyers--it's hard to say that engineers are particularly special in this regard.