Zilean Time Bombs

I know hardly anyone plays zil anymore, but there has been something about his bombs that irks me.

Namely, spell shield interaction. Stuff like sivir's spell shield, noc's spell shield, and banshees. All of these block the placement of the bombs rather than the explosion of the bombs. (haven't tested explosion popping banshees yet)

I think it would make more sense, and at least let the enemy feel slightly better about zil's bombs if they could use their spell shields on the actual explosion rather than the placement of the bombs.

Another thing, it's really annoying drawing turret aggro when I place a bomb on someone. I thought you only draw turret aggro when you deal damage. I've tested putting my slow on the enemy and that does not draw turret aggro, so is drawing aggro on placing the bomb a special case interaction that riot did on purpose? or is it simply the remnants of the outdated mechanic count down timer doing 1 tick of true damage?