"Homebase" is where all the surviving pieces are apparently on their starting squares. Here is a very easy new example proof game: can you find the unique shortest game that leads to this position?
[Title "A.Buchanan 26-11-2020: shortest proof game?"] [FEN "rnbqkbnr/ppppppp1/8/8/8/8/PPPP1P1P/RN2K1NR w - - 0 1"]
Yes c1 is empty!