The NIJ publication is useful for estimating the depth and therefore the volume of standing liquid in a puddles on flat surfaces. Estimating the amount of liquid which may have soaked into plywood is more problematic.

I did some soaking expriments once upon a time and found that typical wood boards burned about the same regardless of the soaking period up to 24 hours. The retained fuel did not produce much flaming.

In his thesis, John DeHaan reported the measurement of evaporation when pentane was poured from a limited height. He found the amount of evaporation to be about 25% during the pouring action and suggested that gasoline and pentane should behave similarly.

The NIJ experiments on wooden floors (parquet) produced surface char as contrasted with the absence of char from gasoline spills on plywood reported by DeHaan in Kirk's 5th Edition. The apparent contradiction in these two results may arise from the relative size of the pours. The relative amount of backradiation is greater for larger diameter spills. This is a phenomenon which needs to be studied and quantified.

I have observed numerous small-diameter gasoline puddle fires on wood, non of which have produced significant charring.