Jevon Hair is a prop created for L'Homme, so it should fit exactly on him if there are no modifying morphs to his head.  I don't understand why the skull cap is prominent in the prerendered images.  Prop hair does not need to conform to its specific model; the vendor embeds morph fits for other models but requires little adjustment to fit correctly.  The hairpiece on the female is showing too much scalp after rendering, indicating that the prop either has the wrong morph fit applied or belongs to another model and was not manually fitted to the head.  I wouldn't consider them vendor flaws.