[Lagged2Death]

This analysis is making a very specific measurement. They're only counting software crashes that are detected and reported in Windows logs.

If a machine crashes so severely that a crash report is not generated, than those reports will not be present in our data. Therefore, our analysis can be considered conservative...

"Conservative" here means "it underestimates the crash rate by some unknowable amount."

If you drop your laptop down a flight of stairs, it will likely develop some hardware problems. But for one thing, not all hardware failures will cause software crashes and crash reports. For another thing, you're likely to just replace the drop-kicked laptop, and the hardware failures will never appear in logs like these.