You're a graphic designer who works on apps and websites
He might also be doing any or all of the following in addition to visual design: requirements analysis, ux design, prototyping, usability analysis, QA etc which would mean that he's involved in "designing a digital product". It's a very different role than somebody who, for example, does mockups of a single-screen landing page. And with regard to your comment about Facebook being a service…a service can be a product, the two are not mutually exclusive, the definition of a product is very loose and is basically anything that is made or grown to be sold or is the result of a process, that can include goods and services. I'm not sure where you got the idea that a product is exclusively a physical object but it's not based on any common English definition.
He might also be doing any or all of the following in addition to visual design: requirements analysis, ux design, prototyping, usability analysis, QA etc which would mean that he's involved in "designing a digital product". It's a very different role than somebody who, for example, does mockups of a single-screen landing page. And with regard to your comment about Facebook being a service…a service can be a product, the two are not mutually exclusive, the definition of a product is very loose and is basically anything that is made or grown to be sold or is the result of a process, that can include goods and services. I'm not sure where you got the idea that a product is exclusively a physical object but it's not based on any common English definition.