I haven’t tracked it explicitly, but I think the breakdown is something like:
10% of games end due to an early advantage (eg Metamorphosis) or concession, with the winner never building a Tech II, and the loser never getting a Tech II card into play
50% of games end with both players at Tech II, having played Tech II cards (or at least tried to - maybe one player’s tech II stuff prevented the other player from getting their own Tech II stuff into play), but not building their Tech III
30% of games end with one player building a Tech III, but not playing a Tech III card. Either because their Tech III gets destroyed and they lose, or because they were already ahead, and the opponent just concedes
10% of games involve one or more Tech III cards being played by one or both players. This usually happens in more defensive games, and around turn 8 or 9.