I can see the battle lines being drawn up now
, depends if you are a "top of head" true believer or "to the eye" blasphemer.
Based on scales as they were used for modelling/model railways long before commercial wargame figures came along a model figure should be a scale representation of a 1800mm high person measured from sole of feet to crown of head. It is set to be the mean value around which given variations are possible.
Thus on a 28mm figure 1mm represents 64.3mm on a real person. So 1/64th scale. That is why 25mm figures are 1/72 scale, 12.5mm figures are 1/144th, 6mm figures are 1/300.
A 28mm figure in 1/56th is only 1m56 tall (5'2") to be true to scale it would need to be 32mm (hence the do you measure to the crown or eye arguments) Similarly a 1/50 scale figure should be 36mm to top of head and a 1/48 37mm.
Although with most 28mm figures it is not the height that determines whether they look to be in scale, it is the bulk of the head and equipment.