`ph` style is not part of the USX 2.6/3.0 rnc schema but is mentioned in documentation

[Rolf-Smit]

According to the documentation on USX 2.5 the ph paragraph style is still valid to use, even though it is recommended to use li instead: https://ubsicap.github.io/usx/v2.5/parastyles.html#usx-parastyle-ph

Same for the USX 3 (master) documentation: https://ubsicap.github.io/usx/master/parastyles.html#ph

However the schema found here: https://github.com/ubsicap/usx/blob/master/schema/usx_2.6.rnc and here: https://github.com/ubsicap/usx/blob/master/schema/usx.rnc

Do not have the ph included as paragraph style, is that a bug? Is the documentation wrong? What's going on?