I am also getting this bug with Wrexham on the first game after being promoted to L2. It forces an empty bench spot, like others have said.
I will often pick my starting 11 and pick quick bench (Pick without restriction -> pick unpicked positions only) and this is also not working in this situation - you get a warning from AM but no additional picks are selected.
Looking around with the in-game editor, players that allow this to rule to qualify seem to have an additional row in "Trained at club" with a null type.
I am also getting this bug with Wrexham on the first game after being promoted to L2. It forces an empty bench spot, like others have said. I will often pick my starting 11 and pick quick bench (Pick without restriction -> pick unpicked positions only) and this is also not working in this situation - you get a warning from AM but no additional picks are selected. Looking around with the in-game editor, players that allow this to rule to qualify seem to have an additional row in "Trained at club" with a null type.