Upon system boot, the udiskie tray, started via systemd unit

[Unit]
Description=udiskie: udisks2 front end
PartOf=graphical-session.target

[Service]
Type=simple
ExecStart=udiskie --smart-tray --automount
Restart=on-failure
RestartSec=10

[Install]
WantedBy=graphical-session.target

causes the tray first to be started in windowed mode. After some seconds (a bit less than a minute - around 55s - upon service start) the window is removed and it shows up in the tray area.
Also it only ever happens after login, as restarting the udiskie unit doesn't reproduce this problem.

Has anyone else seen this?

udiskie 2.5.8, running on Debian testing, i3 window manager, no desktop environment.