I grind my parting tool at a slight angle. The advantage is that the back of the work should be free of a pip or "sleeve". But it does impose a sideways force on the tool, and the swarf is wider than the groove that is being made. This can lead to swarf jamming., and dig ins
With the tool mounted inverted in a back toolpost, this is less of a problem, as the swarf tends to fall downwards.
Howard