Munro has a niche in pro play that is being made even stronger, the guy you pick to punish ap top and jungle. He already did that since they couldn't force him out of lane and the buff makes this even more defined and forces diversity even if he isn't picked because it becomes a choice of picking only 1 of the 2 or risking the enemy picking Mundo.
Tf being viable means that picking a passive midlaner like ori who won't bully him will allow for the enemy to bully the sidelanes heavily, forcing you to keep that in mind and try to get safe lanes around the map if you want to have little pressure mid.
Irelia wasn't mentioned in the post but she is also a champ who will mostly likely be used as a counter, in this case against gnar. Since she will naturally bully him picking gnar becomes an actual risk instead of a safe pick.
Ekko is getting buffed for pro play since he is one of syndra's main counters because of his ult and split push capabilities.
Most of these buffs are targeted at champs that counter the current meta to force diversity through giving a strong counter pick to the s tier, rather than injecting champs into the meta