Interestingly, in AN 5.179, it lists aristocrats before other castes (vaṇṇa or varna):
among aristocrats, brahmins, merchants,
Khattiye brāhmaṇe vesse,
workers, or outcastes and scavengers —
In the suttas you quoted, it says "the aristocrat is best of those people, who take clan as the standard". The word for "clan" here is gotta or gotra, which is different from caste (which has two types of concepts - vanna or varna, and jāti). The caste system from the Hindu scriptures is varna.
Gotta or gotra is an unbroken male lineage from a common male ancestor. Two persons from the same gotta or gotra cannot get married.
From a caste perspective, Hinduism takes brahmana to be the highest caste, followed by khattiya or kshatriya.
However, from a clan perspective, the suttas take the khattiya or kshatriya i.e. aristocrat, to be the best of people (jana).
Perhaps the reason for this is that kings are always khattiya or kshatriya, and their lineage is always an unbroken male line from the first king of that dynasty. Since a king is the best of people in any country, and his clan (in terms of ancestral lineage) is always aristocrat, so aristocrats are presumably the best of people in a country from the perspective of clans (gotta).