Plugin maven, specify the goal without the phase

Question

I didn't understand what is the point of specifying a goal in a plugin without associating it with a phase.

Example:

<plugin>
    <groupId>org.owasp</groupId>
    <artifactId>dependency-check-maven</artifactId>
    <version>7.1.0</version>
    <executions>
        <execution>
            <goals>
                <goal>aggregate</goal>
            </goals>
        </execution>
    </executions>
</plugin>

I read in the documentation of this plugin, that the "aggregate" goal is associated by default to the "verify" phase, but then what is the point of specifying the goal in this way without <phase>?

<executions>
    <execution>
        <goals>
            <goal>aggregate</goal>
        </goals>
    </execution>
</executions>

how does maven understand which phase to associate it with?

Thanks