There are many different types of mutations in the BRCA1 gene. And having the mutation just makes you more susceptible to cancer so even within the same family with same mutation what type of cancer you get can be different since cancer is at its core multifactorial.

I think a better example of this is Achondroplasia caused by a mutation in the FGFR3 gene there are like two very specific mutations that cause almost all of these cases which are usually random and not inherited.

Edit: check out this article about mutation hot spots https://pubmed.ncbi.nlm.nih.gov/27070266/