There has been some question about stock shares in closely-held corporations. Other mediums about which there is some ambiguity include mutual fund shares and limited partnership shares. The revisions remove the ambiguities. The principal determination of what is a security or not remains the form in which the investment medium is issued. But beyond the general definition, Article 8 more specifically addresses some investment mediums.
Shares of stock are explicitly securities.
Limited partnership and limited liability company shares are not securities unless dealt or traded in securities exchanges or markets, and unless the terms of the medium expressly declare them to be so or they are investment company securities. Options and commodities contracts are specifically not securities. Commodities contracts are specifically not financial assets, either. The broader definition is necessary to govern all contingencies. The result is a much more viable Article 8.