Masto.host@inditoot That is currently the expected behaviour for Mastodon.
As to why, I can imagine the complexity of keeping that information in sync across all servers but you would have to ask the development team for a definitive answer.
If you want to see the full up to date information of a user, you need to go to the actual profile page on their instance. Eg: in my case you need to go here: https://mastodon.social/@mastohost
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