Misunderstandings in box2d, what's wrong?

Question

Game development

I'm making a toy on Libgdx + box2d. Simple platformer. Today I encountered something incomprehensible: I make moving platforms using KinematicBody, and I move them using the setLinearVelocity method. I want that when the player stands on the platform, he moved with it. Tried to do the following thing. In the update() method, where all the logic is updated, each frame wrote the following thing:

Array<Contact> contacts = world.getContactList();
        for (Contact contact : contacts){

            Fixture fa =contact.getFixtureA();
            Fixture fb = contact.getFixtureB();

            if((fa.getUserData() instanceof Player && fb.getUserData() instanceof MovingPlatform) ||
                    (fa.getUserData() instanceof MovingPlatform && fb.getUserData() instanceof Player)) {
                 player.p_body.setLinearVelocity(player.p_body.getLinearVelocity().x+1,player.p_body.getLinearVelocity().y);
            }
        }

And I discovered the following - the collision of the player with the platform is determined EARLIER than it actually happens. What kind of bullshit is this? And how to make a normal moving platform?
PS The world is updated like this: world.step(delta, 6, 2);