First semester freshman year, most kids at most schools haven’t even officially declared a major let alone picked a field within a major to specialize in.
At most top math PhD programs, the “kids” have to finish their “qual” courses in the first year, and only then decide what courses to take in a particular field to continue their research specialization.
Expecting a kid to decide in freshman year undergrad, what they needn’t decide until the beginning of the second year of a PhD program sounds like remarkably dumb advice and a great way to drive someone away from the major entirely.