If not--I am very lightweight right now, and I'm trying to put on body mass by eating more and exercising. While my volume will increase, my main growth is in density. My growth is not in fat, but actual muscle mass. Is this growth? If so, I have gone from 125lb to 140lb in ~2 months, which in absolute terms is obviously more than the baby (my goal is 160lb by the end of the year).
A few years ago, I went from ~130lb to 165 lb in three months--blame the free food at FAANG cafes during an internship. But this might be closer to what you were saying earlier--putting on fat.
Edit. I guess in the original statement saying that a person will never gain weight at this rate again there should be the explicit assumption that we're talking about natural growth, not growth due to external factors (ie more eating--intentional or not). In that case, that statement would be true.
But in that sense, of course a baby will have more growth than an adult--isn't it reverse exponential?
Average height at age 12: 59". At age 13: 62". 3" of growth.
At birth: 19". At one year: 29". 11" of growth.
Try matching that just by eating more.
(obviously, yes, it's easier for a small thing to grow than a large thing. But it's still crazy fast. Imagine being 50% taller in a year)