What constitutes the new rule of a "golfer not playing alone?"

Does someone need to accompany me for a round to count as valid?

Yes — a round is valid and the score may be posted if at least one person accompanies you for a minimum of 7 holes and can attest to your score. Acceptable companions include a caddie, a friend riding in a golf cart, an opponent, a fellow competitor, a child, or anyone else who can verify your score.