I can see your point. But those who would like to level Touramoloch over 26 would also be battling with it. That DNA is available in battle incubators and the more you battle, the more you will get. It is the same with the other arena exclusives. It is also a reward with limited player desirability. Longer term/top players will have already level it up and have no need for a huge dump of its DNA. This gives them little incentive to battle to a higher level.
Some creatures are labeled as “Event Only”: Only available during special events or Tournaments. I would think these would be the first choice to have available as rewards for these events. Currently, Rhino and Blue are in demand but not available. For most of the player base it would make better playability to have Tournament rewards be something that is not available readily and worth trying to achieve a higher trophy count to place higher.
In the current game, Rhino would have been a logical choice for a Tournament reward. The hype is high as it is new, and it takes 200 per fuse. Players would be more likely to battle more to get to a higher trophy count to get more of its DNA. Megaloceros would have been another good pick for a reward.
But alas. Looking from The Company point of view, it is better to keep them in demand for Incubator sales.