Gamma as you said is non linear but it affects 1 straddle the same way (1/10) of selling 10 straddles. While moving one point away (or towards) the strikes is non linear - that's not what we're discussing here - we're not discussing that landing 5 points from the short strike is the same as 5x landing 1 point from the short strike - we are talking about the net return and the margin required to hold the position.
It's totally what we're discussing here. In fact Mav and I have made the point that the only sane play here is controlling gamma so you're on the right side of it and that is indeed one of benefits of straddles.
However, the entire thread has NOT been about straddles but about OTM puts and calls that have huge gamma risk - so that straddle example doesn't even apply really. If all you do is sell ATM straddles then good for you but the vast majority do not and continue to stay on the "can't ever be wrong but when I'm wrong I'm wrong big" path.