/spreadplayers and /worldborder <center> arguments don't suggest coordinates

Unlike all other coordinate arguments in commands (/setblock, /particle, etc.), the <center> argument for /spreadplayers and /worldborder center do not suggest the typing player's coordinates or autocomplete them with TAB.

This is likely because they're different from the others – using X and Z only instead of a coordinate-triple. (vec2 vs vec3)