Yeah it's pretty much impossible to plug in incompatible cords to outlets.
The reason I think it would be helpful is when you're viewing a rack
preparing to deploy new equipment it would let you confirm that the power
required is available on the PDU without having to visit the rack.
I only have 11 racks to manage here in the same building so it's not a huge
issue. But I could have more racks in another building in the future and
being able to look in RackTables to confirm exactly which variety of power
outlet is available could save me a lot of time and headache down the road.