cwatters, you're absolutely on the money, though not because any given runway is 'too short', rather, the dynamics involved are so complex that runway length soon becomes irrelevant, as the contaminant does its fiendish work in front of the tyres...
Not to mention the possible effects of wet snow flung up by the NLG trying to put the fires out, or the other odd stuff that goes on in wet snow, for example.
(Strictly, SOPs are not the same as performance calculations, but you're right that this is elementary stuff).