UX literally focuses on providing an optimal experience for the user.

Product goes beyond that and looks at the overall business goals, positioning, competitive analysis, technical structuring of the product (programmatic SEO), cultural factors etc….

Example: You could have an ideal flow that works best for the user - a multi-step form. You design it in such a way that works well.

But, you didn’t consider that the email field should go first because that’s the only way you can recover a user who left mid-way. This is a business goal and doesn’t necessarily fall under the scope of UX, but is vital to increasing signup conversions.