The other day, I noticed that my friend’s Dell laptop had a similar feature but with a shorter fade-in-fade-out period. Its rate was around 40 blinks per second, or the average respiratory rate for adults during strenuous exercise—not very indicative of something in sleep-mode.
As to why Dell didn't copy it exactly... perhaps they reviewed the patent and decided they would get in trouble?
Personally, I think we should not personify our computing hardware. It's a tool, not your friend. When my machine goes to sleep, its lights turn off. If I want to wake it from sleep, I press the power button. If it was off instead of asleep, I would press the same power button. No need for an LED to tell me what's going on.