If you are describing what I think you are describing, I remember specifically seeing this on two mothers. By chance (or not by chance), they were related to one another.  The babies were fat, happy and gaining well.  I called it "straightening the straws" and it may have also had something to do with nipple elasticity, the way breast tissue did not come "into" the nipple, and maybe even a way for the baby to control strong letdown and fast flow.
Maria Paciullo, LLL, IBCLC, JD, MOM
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