To quote that same document:
Figure 5 looks at the average temperatures for different age groups. The distributions are in sync with Figure 4 showing a mostly flat failure rate at mid-range temperatures and a modest increase at the low end of the temperature distribution. What stands out are the 3 and 4-year old drives, where the trend for higher failures with higher temperature is much more constant and also more pronounced.
That's what I referred to. I don't see a total age distribution for their HDDs so I have no idea if they simply didn't have many HDDs in the three-to-four-years range, which would explain how they didn't see a correlation in the total population. However, they do show a correlation between high temperatures and AFR for drives after more than three years of usage.
My best guess is that HDDs wear out slightly faster at temperatures above 35-40 °C so if your HDD is going to die of an age-related problem it's going to die a bit sooner if it's hot. (Also notice that we're talking average temperature so the peak temperatures might have been much higher).
In a home server where the HDDs spend most of their time idling (probably even below Google's "low" usage bracket) you probably won't see a difference within the expected lifespan of the HDD. Still, a correlation does exist and it might be prudent to have some HDD cooling if temps exceed 40 °C regularly.
I generally find that cutting taxes is more popular with the politicians who think that reducing the debt is more important than a functioning power grid and bridges that don't collapse. Don't ask me how the hell reducing tax income is supposed to help with the deficit but it's probably built on the assumption that the ~~kickbacks~~ economic growth will make up for it.