Legal Question in Real Estate Law in California

You're not reading the sentence right. It is not "real property to be formed," it is "contract to transfer real property to be formed." In other words what the sentence means is: "in order for an enforceable contract to be formed, when the contract is for transfer of real property, there must be consideration." To put it in simpler terms, you need consideration to form (create) a binding contract to transfer real property. In fact, you need consideration to form any kind of contract at all. This is opposed to a gift, which by definition involves no consideration.

All of the real property in existence was formed either 6,000 or several billion years ago, depending on your religious beliefs if any.

In England, many centuries ago, most people could not write. To help make sure that an agreement to transfer land had actually occurred, there was the public giving of some form of consideration/payment by the "buyer" of the land. Traditionally, that could be as little [or in addition to a later transfer of money] as a peppercorn [the hard seed of the pepper plant that is ground up to get the black or white pepper spice]. In that way the people living in the area would know the land had been transferred. That part of the old English common law was adopted into our system of law, which is based upon English law. So in order for there to be a contract to transfer real property [land, houses, something that you an physically see but not move], some form of "consideration" has to be given, unless you are giving the real property as a gift to someone.

[not proof read]

It's the contract that's being formed, not the real property.

Consideration, or a legally-acceptable substitute, is necessary for the formation of a contract. Gifts are not contracts, and no contract is required to transfer ownership of real property by gift.

Arguably, real property is still being formed...see for example the Wikipedia article on Surtsey.