Why would any modern day viewers feel cheated? (spoilers)
To an extent I can understand audience in 1950 feeling cheated because the concept of a "false flashback" was totally foreign.
But how can anyone feel cheated at this point in time? The flashback is not a cheat! When we are seeing the flashback Jonathan is clearly *telling* Eve what happened. This is the story he is telling and we are seeing the story on screen instead of just hearing him say it.
Now, this flashback would be cheat if this was the sort of flashback where Jonathon was simply remembering the events to himself. In that case, it would be the type of flashback where we should clearly be seeing what actually happened. But this was not an "Oh, I remember" type of flashback.
This was a "story" being presented so that we see the everything he is saying.
I can't see how people see this as a major flaw... there are other, more serious flaws and if anything, the realization that the flashback was not true was the one thing that won me back.