Yep, it's Canon Law:
§2. In the baptismal register are also to be noted confirmation and those things which pertain to the canonical status of the Christian faithful by reason of marriage, without prejudice to the prescript of can. 1133, of adoption, of the reception of sacred orders, of perpetual profession made in a religious institute, and of change of rite. These notations are always to be noted on a baptismal certificate.
https://www.vatican.va/archive/cod-iuris-canonici/eng/documents/cic_lib2-cann460-572_en.htmlAs far as my mother, I think she's hoping her grandkids can get baptized at some point, so she wants everything in order.