What is the point of Kayn's transformation being EITHER Blue or red?

Before you downvote this because I'm mentioning Kayn, its just a question.

FROM A GAME DESIGN PERSPECTIVE, what is the purpose of kayn have to pick between transformations based on damage done to melee users or ranged? Why not just let him pick whichever form he wants when he's able to transform.

With the average game lasting 27 ish minutes, and Kayn's average transformation time being around the 13-14 minute mark, and a 4 minute timer to pick the OTHER form if you don't get it right away. You're looking at a potential 18 minutes being base kayn, which is relatively useless in comparison to either of the transformed kayns.

My question is what is the purpose of forcing kayn to wait that 4 minutes for a different form? It seems like if you give him a choice of either transformation when he unlocks it, that gives the champion a couple more minutes being useful in games that are getting shorter and shorter by the season.

Also, Why would they design him like that, vs a level requirement (8-9?), or a flat damage amount to enemy champions?

And yes, I understand that the Kayn player should be looking at the enemy team comp to see what form he's likely to get when he transforms at 14 mins. (a mostly ranged team will likely yeild blue kay, mostly melee will be red.)