iFeatures are an old, but powerful Feature of Inventor.
Since the age of this functionality, you can only place iFeatures in already existing bodies, but not start a new body with an iFeature.
Starting a new body with an iFeature like you do e.g. with an extrusion shouldn't be too much of an effort and probably do for a JDI.
This could be very helpful in multi-body-parts.
Also when you want to use iFeatures in Factory Assets.