Well since I'm the author of the drawings I suppose it is prudent that I reply ...
To add to mpoulton 3 wire feeders were the norm to detached buildings for years and are just fine if installed properly. The feeder neutral just did double duty as 'neutral' and 'equipment ground'. The utility only brings 3 wires to your service equipment, the difference is the home owner will never likely fool with those wires.
One issue was other metallic paths existing or being brought to the building at a later date. Bonding neutral to ground allowed neutral current to use these other metallic paths to return to the transformer. Mainly because of improper grounding at the detached structure.
As an example see this drawing