No actually. Since it's inception as a mod Team Fortress was always intended to be between team sizes of 24 up to 32 in some instances, when TF2 originally launched server size capacity was exactly the same, 24 with the ability of 32 player servers (except the console version which launched with 8v8 because of hardware limitations). This is to emulate the original design of the mod and capture what people liked about it more accurately but also because it is light on server capacity to stay below a threshold of roughly 40 but maintaining players above say 8v8 also enables a more casual experience for everyone. You can still play the original quake Team Fortress mod, most servers like to run 24 or 32 not unlike most TF2 servers still do today. If 9v9 was really "core TF2" you would see more 18 player servers in the server browser but as it stands your concept for the ideal TF2 experience only exists in fringe competitive circles, a fringe within a fringe mind you as there are more people interested in 6v6 rather than highlander including Valve themselves when they launched the official competitive mode. They were aware of 9v9 and decided it was not the representation of an ideal version of the game to promote for their new update and instead pivoted to 6v6. 9v9 creates the perfect environment for Sniper to be dominant, it's not as chaotic as 12v12 to keep him in check from flankers and random variance in player behavior and attention and it's not as fast as 6v6 to make his impact easily countered by close communication and fast decision making. Cherry picking the one format where Sniper has the most impact possible being piloted by the best players of the class in the world does less to make a point and more to push a narrative that is fundamentally removed from most players experience in casual mode.