How to force systemd unit to log into journal instead of syslog

Question

For some time now I'm trying to force systemd unit I created to log command output to systemd journal. It logs only to syslog. Here is my config:

$ cat /etc/systemd/system/sf-synchronize.service 
[Unit]
Description=Synchronize Files With GCS Bucket

[Service]
ExecStart=/snap/bin/gcloud storage rsync --recursive --exclude="^lost\\+found/.*$|^.*/tmp/.*$" "/mnt/disks/storage/" "gs://XXXXXX/2023-11/"
StandardOutput=journal
StandardError=journal

This is config of loaded service:

$ sudo systemctl show sf-synchronize.service | grep 'Standard\|Exec'
ExecMainStartTimestamp=n/a
ExecMainStartTimestampMonotonic=0
ExecMainExitTimestamp=n/a
ExecMainExitTimestampMonotonic=0
ExecMainPID=0
ExecMainCode=0
ExecMainStatus=0
ExecStart={ path=/snap/bin/gcloud ; argv[]=/snap/bin/gcloud storage rsync --recursive --exclude=^lost\+found/.*$|^.*/tmp/.*$ /mnt/disks/storage/ gs://XXXXXX/2023-11/ ; ignore_errors=no ; start_time=[n/a] ; stop_time=[n/a] ; pid=0 ; code=(null) ; status=0/0 }
ExecStartEx={ path=/snap/bin/gcloud ; argv[]=/snap/bin/gcloud storage rsync --recursive --exclude=^lost\+found/.*$|^.*/tmp/.*$ /mnt/disks/storage/ gs://XXXXXX/2023-11/ ; flags= ; start_time=[n/a] ; stop_time=[n/a] ; pid=0 ; code=(null) ; status=0/0 }
StandardInput=null
StandardOutput=journal
StandardError=journal
MemoryDenyWriteExecute=no

I've started service few times using sudo systemctl start sf-synchronize.service but there is nothing inside in systemd journal

$ sudo journalctl -u sf-synchronize.service
Mar 01 16:01:58 salesforce-archive systemd[1]: Started Synchronize Files With GCS Bucket.
Mar 01 16:03:59 salesforce-archive systemd[1]: sf-synchronize.service: Deactivated successfully.

Actual command output is in syslog:

$ sudo tail -f /var/log/syslog 
Mar  1 16:02:12 salesforce-archive gcloud[3946]: At file:///mnt/disks/storage/**, worker process 3910 thread 140482368034624 listed 32000...
Mar  1 16:02:23 salesforce-archive gcloud[3946]: At gs://XXXXXX/2023-11/**, worker process 3910 thread 140482368034624 listed 32000...
Mar  1 16:02:24 salesforce-archive gcloud[3946]: At file:///mnt/disks/storage/**, worker process 3910 thread 140482368034624 listed 64000...
Mar  1 16:02:41 salesforce-archive gcloud[3946]: At file:///mnt/disks/storage/**, worker process 3910 thread 140482368034624 listed 96000...
Mar  1 16:02:46 salesforce-archive gcloud[3946]: At gs://XXXXXX/2023-11/**, worker process 3910 thread 140482368034624 listed 64000...
Mar  1 16:02:54 salesforce-archive gcloud[3946]: At file:///mnt/disks/storage/**, worker process 3910 thread 140482368034624 listed 128000...
Mar  1 16:03:02 salesforce-archive gcloud[3946]: At file:///mnt/disks/storage/**, worker process 3910 thread 140482368034624 listed 146597...
Mar  1 16:03:08 salesforce-archive gcloud[3946]: At gs://XXXXXX/2023-11/**, worker process 3910 thread 140482368034624 listed 96000...
Mar  1 16:03:29 salesforce-archive gcloud[3946]: At gs://XXXXXX/2023-11/**, worker process 3910 thread 140482368034624 listed 128000...
Mar  1 16:03:41 salesforce-archive gcloud[3946]: At gs://XXXXXX/2023-11/**, worker process 3910 thread 140482368034624 listed 146597...
Mar  1 16:03:58 salesforce-archive gcloud[3910]: 

I'm running this on VM in GCP using ubuntu-2204-jammy-v20240228 image

$ cat /etc/issue
Ubuntu 22.04.4 LTS \n \l

Other services somehow log into journal but not this one. How to fix this? Thanks