Why is this sample code not using `f:submit`?

[daniel-beck]

I do not understand why the sample code uses basic HTML, when Jenkins has a dedicated f:submit Jelly control:

design-library-plugin/src/main/resources/io/jenkins/plugins/designlibrary/AppBar/index.jelly

Lines 49 to 52 in 5f2c24d

	<button class="jenkins-button jenkins-button--primary">
	Save
	</button>
	<button class="jenkins-button">Apply</button>