Here is the patagraph on page 257 of the book:
R³paloke pana gh±na-jivh±-k±ya-bh±va-dasak±ni ca ±h±raja-
kal±p±ni ca na labbhanti. Tasm± tesa½ paµisandhik±le cakkhu-sota-
vatthuvasena t²ºi dasak±ni j²vitanavakañ c± ti catt±ro kamma-
samuµµh±nakal±p±, pavattiya½ cittotusamuµµh±n± ca labbhanti.
In the fine-material world, the decads of nose, tongue, body, sex,
and the material groups produced by nutriment are not found. There-
fore, to those beings, at the time of rebirth-linking there arise four
material groups produced by kamma—the three decads of eye, ear,
and heart-base, and the vital nonad. During the course of existence,
material phenomena produced by consciousness and by temperature are found”
“The beings in the fine-material realms, being asexual, lack the two
decads of sex, and though they possess the physical forms of the nose,
tongue and body, these organs are destitute of sense receptivity.”
If Bhava dasaka encodes the sex property, or the heart-base encodes the two/three-rootedness, is it still possible for them to change during the bhava from one to the other?
I don’t have a post of you that makes a clear statement, I know only that on multiple pages you describe the evolution of the kammic body and which rupa/dasaka it contains. And since this is at the start of bhava, it should not fundamentaly change during the bhava.