One listing suddenly has “Get it faster” option

I’m selling this product (seller fulfilled), I’m the only seller, and I have only one listing for this product – no variations. Suddenly Amazon added another option to the buy box to “Get it faster”. The price is higher and Amazon promises 5 day faster shipping*

The kicker is that it messes with my order processing because the SKU for this faster shipping is made up by Amazon and not based on my own SKU. So now I have to fix the customer’s order when someone orders it. I can’t find any info on why Amazon does this or how I can turn it off.

Does anyone here know how to fix this?

* I under-promise and over-deliver because Amazon punishes harshly for not shipping on time.