I think you're right, Jeff.

I opened a gazillion Chrome and Firefox windows and your app returned
603. Then closed those and it returned 1.

It would be interesting to build a similar test with Capesoft's
I have a watchdog monitoring some web apps. If anything becomes
unresponsive, Oddjob tries to stop the service in question, then
searches for and kills any running instances showing in Task Manager.
Then restarts the service.

I haven't tried the "250 things" test with it but it's running on a
normal production server that has a fair bit of stuff going on.