Are we to take this as meaning that the product was marketed primarily at women, and therefore men who used it were, well, not being truly manly? Sir Walter says, "Mrs. Clay has been using it at my recommendation", so it's not clear to me whether he uses it himself, though of course none of us would put it past him!

Also note how the ON indicates that perhaps the stuff doesn't really work... because "it did not appear to Anne that [Mrs Clay's] freckles were at all lessened."