Let's say I have a goal of running a marathon, so I decide to start jogging every day. Is my daily jogging a side-effect of my goal to run a marathon? I wouldn't say so. Rather, jogging every day is an explicit course I've set out on with the hopes of achieving my main goal. Daily jogging is a sub-goal of the main goal, if you will. This logic can be applied to the Fed. The main goal is to lower inflation, and the chosen course of action (i.e. the sub goals) are to lower economic growth and to increase unemployment.
A side-effect would be something akin to knee pain. I can't jog without hurting my knees, but having pain in my knees isn't something I explicitly set out to do.
A side-effect of Fed policy would be something like the gilt crises in the UK. Higher US rates increase yields on UK bonds indirectly. But that isn't something the Fed is actively setting out to do.