I assume they're talking about how when multiplying by a matrix by a vector, it's more natural to think of the matrix as a collection of columns than as a collection of rows, and to think of the vector as a column vector.

That layout is a nearly universal convention in applied practice such as statistics. Readers would be very very confused if you flipped it the other way.

The irony is that "programmers" are much more divided on this than statisticians are.