What Clocks said. Imagine if you were to suddenly remove one of the onboard eMMC memory chips--same idea there. I always recommend thinking twice before using an SD as adoptable internal storage, because of this, as well as this increased reliance on inherently lower quality memory chips for more crucial functions. Consumer microSD cards, even from top manufacturers like SanDisk, are still much less reliable than eMMC memory used on the motherboard--just look at the regularity of posts here talking about losing photos on a corrupted card.