So you get a dropdown list from which you must choose a value, while you expect a free text field?

I don't think that this behavior should be changed.

I think, it should. When I enter some text into text field and press Enter, the request must be executed with exactly entered text.

@Aklapper it's already a free text field. You can input whatever you want then change focus (click somewhere outside of dropdown) without pressing Enter key, entered value will stay.