It does not seem to be a direct bug, but a small confusion:
The confusing bit is in [dgt/translate.py (line 3833)]: engine_menu_favorites is displayed on the clock as Special, not Favorites. The web UI separately labels the same category as Favorites in the web client clock.html.
Technical refs:
/opt/picochess/dgt/translate.py:3833
/opt/picochess/web/picoweb/templates/clock.html:2114