I don't think people are "pretending", just that losses are different based on what system you have (not just DC vs AC, but also the voltage, the type of insulator on your cables, the conductor [copper/aluminum, most new stuff is aluminum] and the substations.) Corona losses, specifically, are also strongly affected by the weather! Then you have people writing about it doing incorrect math on some percentage they don't understand from a technical paper.
That said, I agree that 5% sounds close for the transmission losses alone (excluding distribution), and 5% could be easily made up, like you said, by many things, like being next to a wind turbine factory/cheaper land/cheaper labor/tax breaks/many things.
Interesting note: I found here [0] that silver would be a feasible conductor for HVDC lines if prices were lower. On an example line, it would save $19M/yr but cost $18.5B to build, so 1000 year payback time, which is unrealistic. But! If the price of aluminum increased substantially (for example: say we discover smelting releases mega-carcinogens and it's banned) and the price of silver fell (silver is now 4x as expensive as it was in 2003, so I feel like it could fall fairly precipitously) then we could in theory have silver power lines. One thing to remember, though, is that it's only the "skin" of the conductor made of copper/aluminum/silver - the skin carries 90% of the power, but the bulk of the conductor's mass is the cheap steel core that doesn't need to be as conductive because it only carries 10% of the power.
[0] http://large.stanford.edu/courses/2010/ph240/harting1/