Yes, its a very real effect. I also see it most (but not all) of the time. The AI tech trade advantages don't apply to an automated human player for one thing. I think sometimes my civ just lucks into a tech lead or something and in that position it doesn't matter. Also, its kind of a fun challenge to set yourself a goal of playing a ratio of turns. Play 90 turns automated, then take over for 10, automate for 90, etc...