Lol, I thought the same thing, but without the rest of the branches providing nutrients, the lack of chlorophyll in the leaves would either doom the plant, or force it to make new, hopefully green leaves so it can survive. I'd love to have an entire plant that's albino, but nope...
Sometimes abnormalities in nature such as this happen, because
of genetics...
Often when they do people try to cultivate them.
Sometimes they are successful... often they are not.
Like I said... you might wait and see what happens to it.
You might be right in your assessment.
I'm definitely going to let this one keep going as long as possible, if the leaves had been variegated I'd have been even more excited, better chance of a whole plant surviving that way. I wonder if these mimosa can propagate by cuttings very well?