I hold German citizenship, and am traveling from Germany to India. I'd like to visit relatives in the United Arab Emirates, which would work out nicely with my itinerary, but I'd stay over night in Abu Dhabi.
Is a transit visa sufficient here?
None! You do not need any visa to go to UAE for 1 day. You get 90 days on arrival as a German citizen.
You're probably providing incorrect input to Timatic. To me Timatic says this for your itinerary.
Transit - United Arab Emirates (AE)
Nationals of Germany with a normal passport for a maximum stay of 90 days.