Guardian Angel Bug

After playing many games recently with people complaining about instances where isn't working and finally seeing it in person for the first time, I decided to make a recent post highlighting the issue (please, share alike instances).

From looking online and seeing it in person, I believe the bug occurs when user of gets killed during certain spells that have long cc/attack duration abilities (i.e., Ultimate, Ultimate, etc.).

I personally witnessed this effect happen where user had the item passive active before being targeted by ultimate, in which case the user died after ultimate had finished without the item active reviving the user. This is a bug, right?