Good question. There actually isn't a problem with using the exact same variable name in two different functions, as long as it serves the same purpose and stores the same value.
Sometimes doing so makes the code a little more readable.
Why, then, do a lot of my class examples use different variable names for the parameters in the functions, as opposed to the variables that are being passed into those functions?
Mainly because I want students to understand that they really are different variables in each function, even if they happen to have the same names. Otherwise, students see the same name appearing inside both functions and jump to the conclusion that it's the same variable, when it's not. So, my coding choice is for pedagogical reasons.
However, once you are a proficient programmer that understands how variables and parameter passing work, then it's totally fine to use the same variable names in multiple functions, as long as they are really good/accurate/meaningful variable names in both cases.