Yes, the wood is harder around knots. But imho this does not help: a) because the fibers have to snake around and b) because to me it seems best to have a very a most uniform properties in your limbs. Bigger pins in my experience attract chrysals because they are harder spots, diturbing uniform spread of tension and compression, inducing silly peaks. just my feeling 😀 but sonetimes it seems like these pins dont do harm, if small enough...