This is an issue in the new ("ooMenu" based) suggester.
This usage pattern doesn't work any more: Start typing, e.g. "wikida". The suggester dropdown shows up with "Wikidata" at the top. The autocompleted suffix "ta" is selected (orange in my example screenshot) so I can continue typing. If the suggestion is what I want I can simply hit tab and be done.
This doesn't work any more. I need to use the mouse or cursor down to select the first element in the list.
This especially doesn't make much sense if there is only one item in the list. Why not autocomplete it?