Why filtering outside the subquery?

[MikeFilimonov]

https://github.com/mobinni/Complete-SQL-Database-Bootcamp-Zero-to-Mastery/blob/3fa6008ea396a5bcca4180ccdd589500b84785f6/SQL%20Deep%20Dive/Subqueries/answers.sql#L15C1-L15C30

[MikeFilimonov]

vs filtering outside the subquery