Given each major releases provide their own batch of features, deprecation and such, it should become expected that the client no require to constantly look back on older legacy systems just to maintain a sense of backward compatibility.
In fact, some of the "features", if they are unsupported by the server, prevents clients from actively communicating with the server. So even that feature list code isn't properly maintained to keep compatibility with older servers despite the fact the entire selling point of the feature list IS TO DO SO.
Given each major releases provide their own batch of features, deprecation and such, it should become expected that the client no require to constantly look back on older legacy systems just to maintain a sense of backward compatibility.
In fact, some of the "features", if they are unsupported by the server, prevents clients from actively communicating with the server. So even that feature list code isn't properly maintained to keep compatibility with older servers despite the fact the entire selling point of the feature list IS TO DO SO.