Yes this is pretty much true. Even the brown, healthy ones are tough to keep in the beginning but once they acclimate, they do okay. I think the consensus is no one keeps a white sebae alive more than a few weeks. My experiences have both been failures but I also took the hint after the first 2 and stopped trying to keep them. Both of mine were white at the start.
The best you can do is properly acclimate it to your lighting and feed it regularly. Who knows, you may have luck. Others will chime in with their own experiences but white sebae = dead sebae IME.
Some other white host anemones aren't as fragile, e.g.: BTAs or LTAs, even some carpets, but sebae is a tough one. Based on health alone, I think they are harder than ritteri anemones to keep.
I look forward to reading the experiences of the others.