OK, I looked into this some more, and it seems you are right — when the option to display inline autofill menus inside the form fields is enabled, the URI matching is not honored — i.e., the icon/menu is displayed whether or not your vault contains a matching site.
Thus it seems that it would be reasonable to make a feature request to propose that Bitwarden should block the injection of inline autofill menus for all domains on the Excluded Domains list.