I oversimplified in that statement, you need more than a factor of 1 because of heat losses to the environment yes. However 5 is not much different than 1. We've gone from 0.0001 only a few years ago to close to 1 now.

And btw, you really want more than 5, 10 or 20 ideally, but again, that's not too hard as compared to how far we've come and new reactors will be beyond that soon.