WP does not natively support taxonomies for users. I’m not sure that terms are being saved for the user, but I could be wrong. I would check the DB that values are actually being saved.
I can’t find any documentation online of making the count of terms on the admin page into a link to the user list page that only shows users with that term. The best thing I can find is this https://codebriefly.com/how-to-create-taxonomy-for-users-in-wordpress/
I any case, for this to work you would need to use the pre_get_users hook to alter the user query, however WP_User_Query does not support a tax_query. So, even if ACF is saving the terms correctly this information will be useless on the user list page (/wp-admin/users.php). I would say that you could use a meta query here, but that will not work if you are using save/load terms because if this is set then the terms are not saved in post meta. The way I understand it ACF will only save values as object terms or as meta, but not both.
What you need to find, which I cannot locate, is documentation on how to create an archive page based on a taxonomy that is assigned to users. This might give you an idea of how alter the user query in the admin, but as far as I can find this is not possible.
