akali's twilight shroud

twilight shroud is much like twitch's ambush (its a stealth). So why is if she is in the shroud she is no damage from lock on attacks when you lose the vision, such as fiora's ult. Not sure its really a bug or something that needs to be looked at.

From lol wiki: Stealthed units will fade and/or disappear from enemy sight until they attack/have been attacked, or the duration of their invisibility effect expires. For ranged champions, auto attacks must actually land on a target for the stealth to expire prematurely. For some champions, using an ability that will cause them to become stealthed is preceded by a period called a "fade time", during which the champion appears partially transparent, but is still visible to enemies. ***During this fade time, any damage taken by the champion delays becoming invisible for a short period of time. ***No matter how many times a champion is hit, however, the fade time on invisibility cannot exceed five seconds depending on if the champion has base banshee's veil. Summoner spells can be used during stealth without breaking it.