Since the FAQ doesn't give much information, this Stack Exchange answer[1] is more helpful, which links to a paper about liver transplant and includes this quote:

> Regeneration of the liver can be more correctly defined as compensatory hyperplasia where in the remaining liver tissue expands to meet the metabolic needs of the organism. Unlike anatomic true regeneration, the expanding liver does not regain its original gross anatomical structure.

Essentially, it's not the same kind of tissue so it won't work as well for a transplant a second time. I guess you could donate multiple non-translated parts of your liver and the remaining could compensate up to a point, but it's obviously risky and is why no doctor would accept doing a second one.

1: https://medicalsciences.stackexchange.com/a/24438