It's a pop sci analogy, not a rigorous scientific statement. Of course real objects deform, get hot, and lose energy to sound.
But that's the point. Entropy changes. If entropy changes, events are irreversible.
As a crude simplification the less an event leaks entropy, the closer it is to being reversible.
Microscopic events - low-energy atomic collisions and particle collisions - can appear perfectly symmetric in time. So much so that microscopic reversibility is considered a thing in physics and chemistry.
What actually happens is more subtle than that, because quantum indeterminacy makes it impossible to exactly reverse a quantum event. Instead of Newtonian precision you have to settle for a probability density of possible outcomes.
But even so, you can't tell which direction time is running in many particle interactions. The particles aren't altered in any appreciable way, and no information/energy leaks to the surroundings.
So even though the difference between before and after isn't precisely deterministic, you still can't tell whether time is running forwards or backwards, because there's no entropic delta to give you a clue.
But that's the point. Entropy changes. If entropy changes, events are irreversible.
As a crude simplification the less an event leaks entropy, the closer it is to being reversible.
Microscopic events - low-energy atomic collisions and particle collisions - can appear perfectly symmetric in time. So much so that microscopic reversibility is considered a thing in physics and chemistry.
What actually happens is more subtle than that, because quantum indeterminacy makes it impossible to exactly reverse a quantum event. Instead of Newtonian precision you have to settle for a probability density of possible outcomes.
But even so, you can't tell which direction time is running in many particle interactions. The particles aren't altered in any appreciable way, and no information/energy leaks to the surroundings.
So even though the difference between before and after isn't precisely deterministic, you still can't tell whether time is running forwards or backwards, because there's no entropic delta to give you a clue.