Why can't I use ngx.redirect or ngx.say in the header_filter_by_lua phase

[zhyfei]

Why can't I use ngx.redirect or ngx.say in the header_filter_by_lua phase? I have a requirement to intercept download requests, and I have to use the following method.
ngx.header["Content-Type"] = "text/html;charset=utf-8"
ngx.header["Location"] = sso_portal_401
ngx.status = 307
ngx.exit(ngx.status)
Is this approach risky?

[zhuizhuhaomeng]

This approach looks good to me.