Shouldn’t I get the same error? It’s the same situation, assigning a function to a number | Function type and calling it:

type Treta = {
    name: string,
    stuff: number | Function
}

const obj1 = {
    name: "Paulo",
    stuff: () => {}
} satisfies Treta;

obj1.stuff() // No error!

const obj2: Treta = {
    name: "Paulo",
    stuff: () => {}
};

obj2.stuff();
//  ^^^^ ERROR: No constituent of type 'number | Function' is callable.

type Other = number | Function;

const obj3 : Other = () => {};

obj3(); // No error even without satisfies

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