Making something optional on an application is a waste of everyone's time.
If it is optional, and it doesn't have bearing on the application process, then don't ask me to include it.
If it is optional, but it does have bearing on the application process, then I assume that I'm not a good fit for you.
If it is optional, and it officially doesn't have bearing, your screeners and interviewers may still have an internal bias that favors applications which "go the extra step" to do the optional work. Even if they don't, I'm going to assume that they do and that we're all wasting everyone's time in asking me to apply.
If it is optional, and it doesn't have bearing on the application process, then don't ask me to include it.
If it is optional, but it does have bearing on the application process, then I assume that I'm not a good fit for you.
If it is optional, and it officially doesn't have bearing, your screeners and interviewers may still have an internal bias that favors applications which "go the extra step" to do the optional work. Even if they don't, I'm going to assume that they do and that we're all wasting everyone's time in asking me to apply.