[Gameplay Clarity] Baron Nashor should not heal/level up while in combat

I have seen this pop up a number of times in personal play as well as pro play. During a baron fight, if the timing is absolutely perfect, baron will level up and gain HP right when a smite is about to come through. In pro play the casters seem to just shrug it off as "well that's unfortunate!". To the players its a slap in the face.

I don't see why this needs to be an issue... Just pause baron XP gain/regen while he is in combat. If there is some kind of technical reason that baron XP gain/level up cannot be stopped during combat then fine. I have not been able to find a red post on the subject. Time on the game clock should not be something players are keeping track of when in the middle of a 50/50 baron fight. The baron heal can easily cause a game to be lost on a preventable technicality.

Another Example: https://www.youtube.com/watch?v=n5MGh0Ioh5k

Okay This one is definitely my fault: https://www.youtube.com/watch?v=Caw5D1-CQq8

But still the smite is an estimation based on timing with the damage coming through and the heal caused the smite to be just that much off..