Template inheritance: non-dynamic mappings

Elastic Stack Elasticsearch
3

Looks like it's documented correctly after all, I just made wrong assumptions: Index templates | Elasticsearch Guide [8.11] | Elastic

The key is in the last note:

Setting dynamic to false doesn’t alter the contents of the _source field at all. The _source will still contain the whole JSON document that you indexed. However, any unknown fields will not be added to the mapping and will not be searchable.

I'm still not too sure about how Kibana handles this, since I did see those fields pop-up where I did not expect them to. Will look into that and report back (in case anyone stumbles on the same question).