From Merriam-Webster:
1: prejudice or discrimination based on sex; especially : discrimination against women
2: behavior, conditions, or attitudes that foster stereotypes of social roles based on sex
I can understand an argument that the author of the comment said "he" because of some assumption that anyone doing stats must be a man. However I'm making the counterargument that using "he" is a standard default in English and that such usage is not sexist, but rather as a result of how the English language is used.