I guess there would be a lot of variables here. What size was the anemone when it was collected?, was it housed in inferior lighting and if so for how long? Were the water parameters poor? Things like that, or even was it a colonial/clone or solitary anemone? and then what are we talking about here, was it the tentacles that expanded twice there size or the actual oral disk?
In my case I remember my first Bubble tip anemone over 5 years ago, I still have the little tribble. At the time I had poor lighting only 80 watts of normal output, then I got 360 watts of VHO and in less than three months it went from golf ball size to softball size and then split. Thats a pretty big difference golf ball to softball size.
Call it growth, well maybe not, but I have no documentation on the growth rates of anemones, but I can tell you mine more than doubled in size, but it may have been a condition from having been larger but then shrinking do to conditions. Who knows? It just may have seemed to have grown that much.
Thomas