I'm not at all saying that yours are caused by stress. I am mearly pointing out that most anemone splits are a reaction to a stress caused on them. Again, you may have absolutely perfect conditions for an anemone and it still may split...I'm not saying that this cannot happen. In fact, it sounds very plausible that it can. Most of the time when someone comes to this site asking what just happened, most of those times it is the cause of stress. My anems would split because of stress, now they stopped and are about 5" each, minimum.
Also, humans do grow to different sizes not only because of genetics, but very much contributed to environmental factors. If we couldn't change the environment so much around us, we would not see so much variation in humans. We would have much more common traits, much more sectored traits purely genetically determined by environment. The example with smaller eskimos is based solely on the fact that they are less likely to spread out across the land, less likely to introduce outsiders into their lifestyles, less likely to be in contact with the range of people in a more desired and populous place, like most of America.
Yes, girraffes wil be of different heights, but you will not see a girraffe with a 1' neck. The reason, natural selection. Because we change our environment, people that live in the cold and people that live in the heat will not have too much difference in temperatures, have the same capability of having light when desired, need not worry about wind chill, growing more hair to keep warm, etc. You cannot change the color of your skin, but there are black, white, etc. skin colors. These are genetically predetermined, but originally came about due to environmental factors.
So maybe the parent clone(the one you got your clone from) was genetically predispositioned to have a stressful environment that altered its clones in some way to reproduce quicker. I would still say that most biological traits are due to environmental factors, which still brings me back to my point that most splits are caused by stress.
Again, not saying you're stressing your BTA's into splitting. It is more likely from what you've told us that you are giving it a very stable and comfortable environment, one in which it feels comfortable enough to split in.
With the clam example I used, this is absolutely not the only way to have clams reproduce. Without ever changing their environment, they will still reproduce at some point. It is just more likely and more of a guaranteed reproduction by taking the above mentioned steps. This is the main reason I continue to mention stress as the major contributor to BTA's(collectively, not yours specifically) splitting.