I don't have the science to back this up, but I think it's plausible, if we make some assumptions. It's basically 3.5lbs/month.

- 2lbs/month is reasonable for beginner gains [citation needed, but sounds right to me].

- If you're really skinny, you'll get bigger gains.

- If you're training optimally (adequate diet, good exercise volume) you'll get better gains than the average beginner.

- Genetic lottery chances.

- Measuring body fat changes isn't perfect (and there will be changes if you're bulking), so it might not be exactly 25lbs.