Gorillas cap out at 500 pounds are well within the realm of 'medium sized.' And sure they're not trained, which means that a human adventurer is even more likely to beat them in a wrestling match.
IRL, I would not encourage you to try that.
Horses are so much stronger than humans that domesticating cows and horses and bringing their strength to bear revolutionized all of agriculture and warfare across the whole of the ancient world. A horse can casually kill a human by accident.
And this is all fine, actually, because DND is not a simulation engine. It's a game with mechanics that are designed to be fun. Adventurers on foot need to be able to fight colossal dragons, trolls, giants with pointy sticks. A bear should be something you can fight and beat pretty early on. A horse should usually be less dangerous than its rider, unlike IRL. And yes, this is all inherently absurd, but that's the fun. You can't accept that premise of someone punching a dragon the size of a castle to death, and then turn around and say "but as a woman she should be weaker on average because-"