There's nothing wrong with it. Stored procedures, Java, Delphi, Ruby, Python, or whatever can be considered as a business logic layer separated from the data storage. Similarly, you consider your Python controller business layer separate from the web UI frontend.
And if you complain that stored procedure language is not so versatile for the business logic, remember that people have been using far worse languages for that, like COBOL, MUMPS, ColdFusion, ...
And if you complain that stored procedure language is not so versatile for the business logic, remember that people have been using far worse languages for that, like COBOL, MUMPS, ColdFusion, ...