DNS can have arbitrarily many levels of caching, because stub resolvers can be caches and can point to other stub resolvers.

For example, you might have a DNS cache in your OS so that if more than one process asks to resolve the same name (or the same process asks more than once because it doesn't have internal caching), only one query has to be made. That resolver may point to a DNS cache on your LAN (deduplicating queries between devices), which in turn may point to a recursive resolver on the internet, which may itself be caching data from the authoritative servers.

If you replace that with DoH between the application and the recursive resolver on the internet, all the intermediary caches are eliminated, even though they might have had significantly lower response times than the resolver on the internet.