Replacing antispam plugin with IMAPSieve not 100% correct?

I think this page[1] is not correct

If you configure this option:

imapsieve_mailbox1_before = file:/usr/lib/dovecot/sieve/report-spam.sieve

the file report-spam.svbin cannot be created because users cannot write there.

[1] https://doc.dovecot.org/configuration_manual/howto/antispam_with_sieve/#howt...