Or had recently had a bris performed. Typically a bris is performed on the eighth day of life, unless there are medical concerns in which case it would be performed at a later date. As they were born premature, that would have probably delayed a bris being done.
Yes of course in premature babies and also in cases of jaundice or other health issues the bris is delayed. However this is a teeny tiny wound that closes up very quickly and heals with good care within a few days. And I am sure LE can tell a bris scar (it is a professionally done procedure) from some random genital injury.