The errata'd version of page 183 says that in darkness "[a] creature effectively suffers from the blinded condition... when trying to see something in that area". That doesn't say that normal darkness can't be seen through, and the updated phrasing works well enough for natural darkness in situations without a backlight. (It creates more problems when applied literally to "opaque fog" and other opaque heavy obscurement, as it suggests they aren't opaque after all.)Yes, but page 183 of the PHB says normal darkness can't be seen through as well. Does it make you believe normal darkness should be opaque too? The only difference here is that the spell cannot be negated by Darkvision.
Honestly, "it's hard to imagine" isn't a very compelling argument.
Similarly, the transparent interpretation of the Darkness spells works well enough in situations without a backlight. But since, unlike natural darkness, the spell can be cast in well-lit areas, the backlight problem would be far more acute with the spell that it is with natural darkness.