K&N not recommended by chevy!

ive talked to chevy service department, he said they do not recommend k&n products because of the oil in it, i had one in 5 diff. vehicles and never had a problem. K&N says it will not hurt a chevy and stand behind there warranty policy. So my question is why does chevy seem so against K&N or any oil based filters, or air intake product. I also asked if they recommended air intake systems and they said they did but it was the ones made by GM , but they dont make anything for the cruze! So whats your thoughts?