Why username is not always in the apache log?

I have setup Nextcloud 18 in docker. NC is behind a ngnix reverse proxy.

Everything is working fine, except logging.

192.168.0.1 - - [14/Apr/2020:20:12:52 +0000] "GET /ocs/v2.php/apps/notifications/api/v2/notifications HTTP/1.1" 200 817 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:75.0) Gecko/20100101 Firefox/75.0"
192.168.0.1 - my.username [14/Apr/2020:20:13:12 +0000] "PROPFIND /remote.php/dav/files/my.username/ HTTP/1.1" 207 1114 "-" "Mozilla/5.0 (Linux) mirall/2.6.4git (Nextcloud)"
192.168.0.1 - my.username [14/Apr/2020:20:13:19 +0000] "PROPFIND /remote.php/dav/files/my.username/ HTTP/1.1" 207 1094 "-" "Mozilla/5.0 (Linux) mirall/2.6.4git (Nextcloud)"

In the log I have the NC username for request from the desktop client (Mozilla/5.0 (Linux) mirall/2.6.4git). However the log does not contain the username (-) when connected from my web browser running on the same computer.

Is it the normal behavior ? If yes what is the explanation for that. And if no, what should I try to fix it ?

Thanks.

I kept searching but I couldn’t find a good answer about that. Is that normal that apache log file does not always contain the user name ? I updated to latest docker image and it still shows this behavior. If it’s normal, then fine. But I’d like to have a confirmation. Thanks.