Static in Swift Protocols

In « The Swift Programming Language (Swift 3). », they start Protocol chapter with this example :

protocol SomeProtocol {
    var mustBeSettable: Int { get set }
    var doesNotNeedToBeSettable: Int { get }
}

Then, they make a statement contradicting this example :

« Always prefix type property requirements with the static keyword when you define them in a protocol. This rule pertains even though type property requirements can be prefixed with the class or static keyword when implemented by a class: »

With the following example

protocol AnotherProtocol {
    static var someTypeProperty: Int { get set }
}

But 2 lines later, they give another example without static :

Here’s an example of a protocol with a single instance property requirement:

protocol FullyNamed {
    var fullName: String { get }
}

So, is static compulsory ? Is it compulsory only when property is settable ? What is the consequence not including static keyword ?

Or do they simply mean to use static and not class keyword.