clarification on omitting fields property

[bossie]

This sentence says that, by default, every Item field is to be returned.

By default, STAC API endpoints that return Item objects return every field of those Items.

However, the rest of the document seems to suggest that not specifying a fields property, will only return minimal STAC Items.

Can this be made clearer? Specifically, what is the behavior of a GET request without a fields parameter?