But for chess, the spread in number of moves is a lot larger, and the branching factor is higher. 20 more half moves and a branching factor of 35 isn’t unreason

But for chess, the spread in number of moves is a lot larger, and the branching factor is higher. 20 more half moves and a branching factor of 35 isn’t unreasonable, and gives you an underestimation of over 10³⁰. And these tweaks do not complicate the math.