be aware every lack of contunuity in your curves - i.e extra points, curves which consist of several pieces will invoke problem with tangency like the one introduced by you. it better to use splines, conics are, single elements for curve
anyway - creo gives you control over the direction of created automaticaly tangency
in dashboard of boundary blend tool swith to Constraints tab, and next pick Display Drag Handles.
As a result control arrows will be displayed with default value 1. please pull this arrow to invert tangency direction or simply change value to -1