Is this a bug?

[Qwerty Quazo]

When I launch a random steam game from a taskbar shortcut, it first opens steam, then the game. With Particle Fleet, it opens the game, closes, launches and steam says I have 2 copies of steam running.

[knucracker]

I'm not seeing behavior like that in testing I just performed...

Maybe do a full system reboot and see if the behavior changes.  Steam tries to make sure two copies of the same game aren't running at the same time.  It also makes sure the steam client is running so it can do authentication, steam cloud stuff, achievements, etc.