I agree, the odds should be 50/50 for pea and single comb when Pp breeds pp.What I can’t follow is the odds. Wouldn’t the odds be 50/50 or better when Indo breeds to the straight comb to get straight combed offspring? What I’m seeing is only one in every few dozen are coming out straight combed.
Ratios can be really off when you have just a few chicks (like when 4 chicks come out the same gender as each other), but if you have several dozen chicks from Indo and single comb hens, that should be enough to see quite a few single combed offspring.
https://www.backyardchickens.com/threads/partial-pea-combs-from-single-comb-parents-help.1332195/
This thread might shed some light on it. (Took me a bit to track it down, but I was sure I'd read something before about pea combs looking like single combs-- maybe that's what happened to Indo's son?)