The omnibox gets autocomplete recommendations which is a very useful feature, how do you expect they could get autocomplete recommendations without sending the prefix to the server? You can also easily disable the feature in settings, it's even right on the front of settings not buried.
Edit: Also if you change your default search engine to Bing, then Chrome is behaving as a keylogger for Microsoft by your definition.
The feature as written indeed can't work without sending every keystroke. That doesn't mean it's any less intrusive. I'd even dare say it was probably not accidentally designed that way.
Edit: Also if you change your default search engine to Bing, then Chrome is behaving as a keylogger for Microsoft by your definition.