Wait a minute here. It's not like you have the ability to tell the input to drop to 0.7V after startup. The feature is designed to keep the system working after startup at 1.1V down to 0.7V. You realize that when the input drops to 0.7V, the chip has to work harder to compensate for the drop in input voltage. I can't imagine that you would actually want to work on the edge like that since you would be on the brink of failure pretty much all the time. A couple of millivolts of ripple on the input and your output will collapse.