user updated_since with attributes

I can't user updated_since in comination with the attributes filter as suggested in examples:

?attributes[]=first_name&updated_since=2022-12-24T08:15:30 will yield 3 employees, ones that had their first_name changed since 2022-12-24T08:15:30:

When I only search withouht attributes and &updated_since=2022-12-24T08:15:30 it works out fine. What am I doing wrong?

Thank you!