There are two levels of objection. The first is the variation in biological response and the second is the lack of proper testing that results in standards which are reproducible for unknown samples. Let us review some of the notable variables that modify the appearance of bruises. The amount of attachment to underlying tissues. Bruising around eyes is much more pronounced than skin overlying thick muscle.
Vascular tissue covering bone bruises more.
Increased age is related to slower healing. Women may bruise more easily than men. Hypertension and blood dyscrasias may alter the extent of bruising. Steroids can alter the dispersion rate of bruising. Deep subcutaneous injury can prolong healing time.