Illaoi E Vs. Morgana spellshield

It really feels like a bug that Illaoi's E gets negated if morg spellshields the cast. It's not CC and it doesn't do magic damage and I can't think of any other non-disabling spells that are entirely canceled by a morgana spellshield. I understand that she can't spellshield once the spirit is taken out but I really don't get what the logic if there is any behind the spirit failing to get hooked in the first place if the shield is there. LIke wouldn't it be weird if Zed ults someone and morgana puts spellshield on them so they don't get marked? That wouldn't make any sense, it's not banshee's veil/sivir/nocturne spellshield.