Two Surveys, Two Different Answers

Because both samples used $n = 400$, $p$ must equal their average, $0.445$.

$p$ is a random quantity that took the value $0.46$ for Researcher A and $0.43$ for Researcher B.

$\hat{p}_A = 0.46$ and $\hat{p}_B = 0.43$ are two statistics; $p$ is a single fixed unknown parameter, and the gap between the two estimates is sampling variability.

Two correctly drawn random samples of the same size from the same city must agree, so the disagreement proves one sample was not truly random.