If I use the following command command:
/give @p minecraft:tipped_arrow 1 0 {CustomPotionEffects:[{Id:8,Amplifier:0,Duration:3600}]}
I would expect to get an "Arrow of Leaping".
Instead I get an arrow Identical in every way to the arrow of leaping, (colour, effect, duration etc) but named "Arrow of Splashing"
I would even have expected them to be named according to effect if they had a different duration, amplifier or were of an effect currently absent from the creative menu, but that's less significant.
The use of numerical IDs is deprecated. Please retry with an effect name.