the main reason imho to keep the mention of such things is that such did exist as such in middle english as well as historically in the other west germanic dialects even though many such as low saxon dialects and many modern high german dialects have lost or are in the process of losing the genitive case and low franconian dialects primarily preserve the entire case system in pronouns retaining just the nominative and the genitive true genitive case not genitive clitic s in normal nouns on the other hand i think that the ideas of genitive pronouns and possessive adjectives should be kept seperate considering english has both considering that they're separate in both english and in west germanic dialects in general if they have both dec utc