Most perpetual motion ideas tend to break because reality does not consist of spherical cows
That’s not true. The first and second laws of thermodynamics tend to be apply even with ideal objects. It’s true that an idealized pendulum is a perpetual motion machines of the third kind and they don’t exist because of friction, but the category exemplified by a pendulum is not interesting and isn’t what people usually mean by perpetual motion machine.
Moreover, any amount of friction will eventually stop a pendulum, whereas something that is supposed to generate a definite amount of energy or decrease entropy by a definite amount will not be stopped by an arbitrarily small amount of friction or an arbitrarily small deviation from sphericality. But in practice you can make things arbitrarily close to perfect.
That’s not true. The first and second laws of thermodynamics tend to be apply even with ideal objects. It’s true that an idealized pendulum is a perpetual motion machines of the third kind and they don’t exist because of friction, but the category exemplified by a pendulum is not interesting and isn’t what people usually mean by perpetual motion machine.
Moreover, any amount of friction will eventually stop a pendulum, whereas something that is supposed to generate a definite amount of energy or decrease entropy by a definite amount will not be stopped by an arbitrarily small amount of friction or an arbitrarily small deviation from sphericality. But in practice you can make things arbitrarily close to perfect.