It wouldn't surprise me at all if the data Marissa looked at was skewed because the corporate Yahoo VPN was atrociously terrible.
People who routinely worked outside of the office, or just wanted to be able to read their e-mail at home without the VPN client randomly panicing their system, had devised various workarounds to get things done.
The corporate VPN is distinct from production, so you could still do actual work without using it too.
I'm stating the fact that when I worked at Yahoo, one did not need to utilize the VPN to connect to production (which is where most staging / pre-prod environments existed as well).
Someone whose job pertains to operations does the bulk of their daily work on actual production hosts, for instance. Some tools (like the bug tracker) also didn't require use of the VPN.