The games famously feature the Pokedex, a running feature that gives you canon information about Pokemon. It is wrong. Here we will explain why.
Firstly, how you may ask can the Pokedex be wrong. It's definitive. Let me hit you up with some entries off the top of my head:
Wailord's length is 47 feet 7 inches and its weight is 877.4 pounds. This is about the length of an orca, but orcas weigh about 10 tons (20,000 pounds). Wailord, by comparison, is less dense than air.
Ponyta's hooves are said to be 10 times stronger than diamond.
Charizard are less tall than the average human male, just 8 inches longer from head to tail than Dunsparce.
Larvitar need to consume an entire large mountain.
I could go on and on but the point is, the Pokedex entries will lead to a ridiculous world if all of them are considered to be absolutely true. There is, however, an alternative.
Certain Professors send out trainers to catch Pokemon for study and compile a pokedex based on the findings of those trainers. Since they're sending trainers out to gather basic data for the pokedex, we can assume that basic data isn't already widely available. Meaning even the most basic scientific research hasn't been performed on Pokemon. And suddenly, when you catch a Pokemon, all that data is entered, as if by magic.
There are two reasons for this. One, Pokemon are convereted into data and back, so it's possible some information could be gleaned about them purely from looking at their code, just as it could be by examining their DNA. But beyond that, most of the information in the Pokedex is probably gained from legend, theory, anecdotes, and isolated facts that is the best information available but not very reliable. Giving this information to the trainers before they encounter the Pokemon for themselves could prejudice their observations. Instead, only after a trainer has worked with the Pokemon are they presented with the pokedex entry that may or may not be reliable.
So why, if Pokemon are so ubiquitous and important, have they not been studied scientifically very thoroughly? Especially since humanity has reached scientific achievements beyond things in our world. Perhaps it has to do with the semi-magical nature of Pokemon. Clearly, they're not entirely beholden to the laws of physics. Look at the difficulty of doing medical studies in a scientific manner in our world. Science requires that what you're studying not behave differently just because you want it to do something or think it should. But humans' bodies work differently based on what we expect and believe, what we want and what we fear. It introduces all manner of error into the study of humans and medicine.
Now transfer that to Pokemon. What if their attacks are stronger or weaker depending on how much they believe in themselves? What if their trainer cheering them on makes them able to stand up to stronger blows? What if a bond of friendship and the determination to succeed are just as important to a Pokemon's performance as the physical makeup of its armor and the chemical properties of the substances it excretes? From the anime, would we expect anything less? Now try to analyze such a creature with the scientific method. It'd be a pain wouldn't it? It would require a very carefully-formulated approach, much more nuanced than combining chemicals and getting a reaction.
Anyway, this bit of fanon lets you take the Pokedex with a grain of salt, treating Pokemon as being the sizes your brain tells you they are rather than the listed sizes, or ignoring potentially game-breaking entries.