I am saying it because I know it to be true. Someone later asked why LCD factories would invest in cleaner rooms than CPU fabs, and I explained the logic.
I think you're expecting some sort of first-principles argument as to why that ought to be true (or worse, asking someone to waste a bunch of time digging up a public citation on the details of factory design), which you're not going to get handed to you on a silver platter. To put it bluntly, if you want to think about it from first principles, go for it, it's not that hard. If you want a source for something covered under NDAs, you can go do the work yourself.
I think you're expecting some sort of first-principles argument as to why that ought to be true (or worse, asking someone to waste a bunch of time digging up a public citation on the details of factory design), which you're not going to get handed to you on a silver platter. To put it bluntly, if you want to think about it from first principles, go for it, it's not that hard. If you want a source for something covered under NDAs, you can go do the work yourself.