Ah yes - it was added 11 months ago by "Smudge the Cat".  It'd be interesting to know what the current situation is.
Bus gates tend to get handled by conditional restrictions on the road itself - see https://wiki.openstreetmap.org/wiki/Conditional_restrictions for that.  In this case https://www.openstreetmap.org/way/552174846 already has "motor_vehicle=no; psv=yes".
