Indeed, Mel is (was?) real and we have a photo of him! If we go to Wikipedia for the LGP-30[0], it links to a wiki article on "The Story of Mel"[1] which names the titular "Mel" as "Melvin Kaye" with a citation, linking to a PDF scan[3] of an issue of "The Librazette" where on the first page, the photo on the left, in the very back and named last of all the people in the photo, is [sic]"Royal-McBee Applications Engineer Mel Kaye" standing and smiling in an all-white shirt.
[0] - https://en.wikipedia.org/wiki/LGP-30
[1] - https://en.wikipedia.org/wiki/The_Story_of_Mel
[2] - https://en.wikipedia.org/wiki/The_Story_of_Mel#cite_note-Lib...
[3] - https://www.librascopememories.com/Librascope_Memories/1950_...