Migbot extruder loading
If the question is "has anyone seen..." my answer is yes. It's not precisely what you show in the drawings, but close enough and for the same purpose.

In the case of a Robo3D R1+ printer, replacing the stock "hexagon" hot end with an E3Dv6 hot end provides for a piece of PTFE tubing inserted into the heat sink. The recommendation from the denizens of the 'net is to slice the top of the tubing in the shape you have in the drawing and to have the tubing extend sufficiently to reach the junction of the hob gear and pinch roller. This took some doing, but I was able to get an appropriate taper to the tubing end that does not contact the moving parts.

As the fed-in filament exits the assembly, the small gap between the wheels and the tubing gives the filament nowhere else to go but into the heat sink and hot end.

As your design reference indicates a 3D printed part, it might be practical to engineer into that segment a larger hole to take the PTFE tubing and then size the length after the wheels are in place.



The above image shows the added PTFE tubing surrounding the filament. Even though the slightly diagonal cut appears somewhat as a cone, it is not. The edges are parallel to the rollers/hob gear. The lower portion has been omitted for ease of drawing, but would extend into a hole drilled or printed in the block holding the assembly, based on the thingiverse link provided.