Ok, whatever suits you. All we have on hand is a sapphire crystal on the back (that’s what Apple calls it in their spec) up until you can show a material analysis that proves different.Still not buying it.
The sapphire crystal on the front of the watch is and always has been far better quality than the backs. Any "sapphire" on the back is just an additive in small quantity, and it's got to be "sapphire" in the same way the iPhone's camera lens is sapphire. (Mine's scratched just from pocket lint.)
Apple may have just enough sapphire in there to legally call it sapphire crystal, but it's not sapphire crystal.