Sivir spell shield VS Morg ulti.

Ok I main Morg and have come across this a few times but when entering a team fight with a sivir on the enemy team if Morg ultis just after sivir shield the ability is blocked.. i get that no problem.. however her shield seems to cancel the ulti all together so her teammates are not tethers as well.. and well u can imagine what happens from there.. so if this a but? was her shield meant to block this entirely for those around her?? like i said.. i have only seen this a few times over the years of playing her... and no.. no one had banshee's veil..