iFly can auto-track in two ways. One is to center your ownship without skewing the map in any way, which is the option you're asking about--no matter what direction you fly or how fast you go, your ownship is pinned in the middle of the screen.
The other option allows iFly to skew the map to show more of the terrain in front of your ownship and less of the terrain behind it. So, if you're flying in "track up" mode, then as you start moving, your ownship will drift down toward the bottom of the screen and settle about 3/4 of the way down, so that 75% of the map is showing what's in front of you, and 25% is what's behind you.
Similarly, if you are in "north up" mode and you're flying to the southeast , your ownship will drift up to the upper-left corner of the screen so that you can see more of the terrain you're approaching below and to the right of your ownship.