KNN Variance using a high value of K and cross-validation
It's just an example in the article trying to make the point that a small change with regards to the age of $p_{11}$ from $30$ to $32$ has relatively large impact on the prediction since with $k=1$ for

$age_{p_{11}}=30$, the model would predict $heigth_{p_{11}}\leftarrow heigth_{p_{3}}$ and for
$age_{p_{11}}=32$, the model would predict $heigth_{p_{11}}\leftarrow heigth_{p_{9}}$.

Moving $p_{11}$ to $age = 50$ would just not serve as a good example for the case they are making because it's not surprising that a model predicts different height values for $age=30$ and $age=50$.
To phrase it differently, the relation between $p_{11}$ being at $age=30$ or $age=32$ is that it's only a small difference in terms of age.