I'm not sure what they are. But, I do know, there was a time when my gigantea and haddoni touched each other in my tank for a couple months, neither one cared. Each day it seemed one flopped over the other, or visa versa. So, even though they weren't the same species, they could touch with no effects, until I seperated them. In my mind, that doesn't matter (sorry Minh, no offense, just my experience).
I also don't believe everything I read, see, hear, or am told. I've violated several "no no's" everyone touts... I'm not sure if that book Phender is refering too is right or wrong. (sure would be nice to know though, I've never read it myself)... There seems to me to be too many unknowns in this hobby. To me, the purple anemone's don't look like the crispa sebae I traditionally think of, that's why I'm not sure myself, asked, and would love to know. When I hear or think sebae, I think of that giant sebae in "davocean's" tank (I hope you don't mind me referencing you).
I just wish someone would chime in with solid evidence/knowledge in what they are....but, we'll probably just get opinions... That's all good too....