You are referencing a book written in 2008 and published in 2009. LLewellyn's 9th edition. Knowledge has certainly evolved in 5 years. Besides that lets break down the statement. "MAY" meaning possibly (possibly not), "SLIGHTLY" meaning a small amount. So possibly reduce your gains by a small amount. Is your health more important than the extra "slight" amount of weight gain? I would certainly sacrifice a pound or two (not saying I agree that I would be) to insure my short and long term health. Unless you don't mind diabetes, heart disease, or cancer. High estrogen raises the risk for all of these among other things.
It is my opinion that any "additional gains" you get from skipping the AI are water weight that you will subsequently lose anyway. So you've exposed yourself to real damage for a few pounds of water weight that won't last.
Just out of curiosity, did you get vaccinated as a child? If you have children would you get them vaccinated or just roll the dice and figure you can deal with polio or small pox after the signs show up?