Both MySQL manual and MariaDB KB describe (in identical words) how unqualified table and view names are resolved within CREATE VIEW statement:
Unqualified table or view names in the SELECT statement are interpreted with respect to the default database. A view can refer to tables or views in other databases by qualifying the table or view name with the proper database name.
However, neither explains what happens with unqualified function names, and it is not obvious, as it apparently works differently from table and view names:
So, it actually uses the function from the same schema where the view resides, not from the default schema. It works the same way in all MariaDB and MySQL versions, so I hope it's intentional and just needs to be documented.