Agreed - I’ve been away for over 4 years now, but I cannot think of any reason SS would be doing protective details for SCOTUS...Even if hypothetically a joint POTUS/SCOTUS event were to take place off fed property, protocol requires your own individual (Or Agency) protective detail be with you. Facility protection may fall to someone else, but not to personal protection.
Don’t Monkey any credit. It’s kinda easy to confuse guys in suits in a protection details of government officials. It’s not very well known that US Marshals protect Supreme Court justices.