How is this incompatible with a product that comes with minimum guarantees? Say we have a way to grade bamboo (this is the question mark in my argument). Grade

How is this incompatible with a product that comes with minimum guarantees? Say we have a way to grade bamboo (this is the question mark in my argument). Grade X bamboo would support the floor in question. Grade 10X bamboo would support 10x the floor in question. For the floor in question, use Grade 10x bamboo. I mean, it seems like something similar must be going on in structural lumber. Take 2x4s for example. This is one piece of wood out of a tree. There must be natural variation across the population of trees providing wood for these. How do we handle that except by saying that this piece of lumber meets minimum guarantees but may be stronger than that minimum, and is statistically likely to exceed the minimum.