Nerub-ar Palace has an instance flight map.

[greerga]

Similar to Sanctum of Domination Sepulcher of the First Ones, there are flight paths inside the beginning raid that do not currently work properly. This is noticeable in the first LFR wing.

[greerga]

I'm thinking the answer is:

            if IsInInstance() then
                local _, _, _, _, _, _, _, instanceID = GetInstanceInfo()
                -- Not "Sepulcher of the First Ones" (2481) or "Nerub-ar Palace" (2657).
                if instanceID == 2481 or instanceID == 2657 then

Will test next LFR/raid run that I do.

Edit: Yes, that works as expected.