> But in Bayes' formula, their plans if something else had happened cannot ever affect how we adjust our inferences

That's not how statistics works. Frequentist p-values and Bayesian inferences are both entirely dependent on the mathematical model in question. "Their plans if something else had happened" are a key part of the model. What you're describing at 2 entirely different experiments:

1) A couple has children until they have 1 of each gender. they have 7 children. How likely is a result this extreme (or greater)?

2) A couple has 7 children. They have a gender ratio of 6:1. How likely is a result this extreme (or greater)?