As far as I can tell, the origin of this phrase comes from (1) people noticing that in Greek, the verb γράφω (grapho), whose primary meaning is "to write" is also used for painting, drawing, etc. (hence icono*graph*y), combined with (2) an idea that developed in the 20th century Byzantine iconographic revival that iconpainting is not art, but rather a form of "language in color" - meant to appeal more to man's intellect and spirit than to his senses.
The first issue is resolved when we remember that vocabulary in one language rarely has a 1:1 relationship—the exact same semantic range—with the equivalent word in another language. Γράφω has a much wider semantic range in Greek than does "write" in English. Hence my reference in the OP to cartography, discography, photography, etc.
The second issue is harder to disabuse ourselves of, since it appeals to the sense of iconography as more mystical, etc., than academic or other forms of painting. But, as a friend of mine recently observed, it's ultimately a kind of gnosticism. Man's relationship with God certainly goes *beyond* the senses, but it doesn't (ordinarily) bypass the senses, and therefore it doesn't circumvent the role of artistic skill and true beauty
This points to a problem in what I call the "Icon-writing Industrial Complex" — all these weekend retreats and workshops where people with zero prior ability or training in drawing or painting are encouraged to "write their first icon" as a kind of spiritual exercise. This may be harmless as far as it goes, but it becomes a problem when they come home and present their icons to the parish priest and expect him to hang it up in the church