I think it's kind of an unspoken admittance of guilt to come forward right away as that may point to someone who's the most guilty with nothing defensible with the most to lose.
I think your right too that soon the 4th or 5th perp to come forward may have waited too long.
And is it possible to have too many perps muddying up the waters with too much data that's different but not real essential like you said?