I've heard this comment about the sharp edge inducing stalls but don't understand why this would be the case. As for the undercamber being originally copied from bird wings, I have my doubts about this type of story. I think the early builders were a lot more methodical than this...and in fact, most of the early ideas about airfoils came from experience with the kites and gliders (manned and unmanned) that were the precursors to powered flight. Originally, these "kite wings" were in essence just "curved single surfaces" which eventually developed into "curved double surfaces."

Regarding the use of "fat wings" to avoid needing functional rigging, my feeling is that, if you don't want to have rigging, you shouldn't be modeling aircraft that needed it. That's sort of like me wanting to build WW2 stuff but complaining about retracts.