is alt+Rightclick the same as the sniper mode ?

By the name it seems to be the same but when I play it don't act the same.

Alt alrightclick (attack move) : unit first want to group together and then do the attack at maximum range :not always the case... Sometime it did it sometime not. Bug ?

Sniper mode : unit go at wanted point directly even if they are not grouped together. I don't see any different with default attack mode.

Is it normal ?