The size of the monsters are comparatively small compared to many creatures on this planet. If they are that small, why are they called monsters when many of earthly and large creatures are not considered as monsters?
Let’s have a comparison, in ascending order, of a list of creatures on earth:
THE GREAT WHITE SHARK
The Great White Shark averages 3 - 5 m long, and is considered the 5th largest carnivorous predator to exist at the moment.
THE ORCA (KILLER WHALE):
The Orca is the 4 largest carnivorous creature on earth, but is not considered a monster, but is instead celebrated as a friendly “free Willy” even though it is known to eat humans without discrimination, and have an intelligence on par with us, but cannot attain technology due to its lack of prehensibility.
Megalodons have been taught to be long extinct for a long time already, but have recently been spotted and found to be alive across many sights on the world. It reaches up to 10 to 15 m in length.
THE BLUE WHALE:
The blue whale, a vicious predator known to devour any creature it sees, even sharks, is 30m in length and is considered one of the largest creatures on this planet, far larger than any monster in Evolve.
The Bloop is a creature detected only recently due to its call being picked up FOUR THOUSAND MILES away from its location, and is estimated to be around 10 times the size of a Blue Whale, or 100 m in length. Below is the sound that was picked up:
In a recent controversial finding, the USS Valkyrie was spotted to be adjacent to what seems to be an ancient Megalodon (though nobody got hurt because it left. The size of the ancient Megalodon is estimated to be about 1200m in length. See illustration below for a comparison compared to the BLOOP.
Even larger creatures are believed to exist, but have not been found yet.
However, the point being, a 10m tall monster is just too small, and there should be a stage 4 monster that is about at least 500m high in order to be considered a real monster.