I'm not familiar with all types, but most pressure treatments don't attempt to stop water uptake, they just impregnate the wood with pesticides/fungicides. It'

I'm not familiar with all types, but most pressure treatments don't attempt to stop water uptake, they just impregnate the wood with pesticides/fungicides. It's not there to stop the water, it's there to stop termites, fungi, mites and other pests that can degrade or threaten the integrity of wood. That's why most exterior decking should be sitting on something like this (https://www.amazon.com/Simpson-Strong-Tie-ABA44Z-Gauge-20-Pack/dp/B002LOT0TA?ref_=fsclp_pl_dp_5 https://www.amazon.com/Simpson-Strong-Tie-ABA44Z-Gauge-20-Pa...) to prevent water uptake. I'd be curious to see how this compares to treated wood for their mold test, though. That seems like a really valid test.