Can confirm for minecraft 18w06a
Confirmed for minecraft 18w03a
Just ran into this now. I think a better system would be to define a bounding box for the particles
/particle <particle name> <start location> <end location> [speed] [count] [force:normal] [viewers]
The main difference would be that this would allow you to use relative positions for the box, instead of just constants as the current system uses.
I can confirm for minecraft 18w07a