When a customer saves a design, he/she can access that design from a different product page.
It loads the saved FPD product and design, but does not load the WooCommerce-product.
They can design expensive products, and lot it on a cheap one, to cheat the price and pay less.
Yes, the name would be different, but it would create a lot of confusion when we handle order and produce the item.
I think you have this problem when you store the users designs in the account of the user by enabling "Account Product Storage"?!
Do you have this option enabled? See screenshot.
Fixed in V3.6.5