In Chapter Ten of Deathly Hallows we are presented with the story of Kreacher's escape from Voldemort's cave:
“How did you get away?” Harry asked, and he was not surprised to hear himself whispering.
Kreacher raised his ugly head and looked Harry with his great, bloodshot eyes.
“Master Regulus told Kreacher to come back,” he said.
“I know – but how did you escape the Inferi?”
Kreacher did not seem to understand.
“Master Regulus told Kreacher to come back,” he repeated.
“I know, but – ”
“Well, it’s obvious, isn’t it, Harry?” said Ron. “He Disapparated!”
“But... you couldn’t Apparate in and out of that cave,” said Harry, “otherwise Dumbledore – ”
“Elf magic isn’t like wizard’s magic, is it?” said Ron, “I mean, they can Apparate and Disapparate in and out of Hogwarts when we can’t.”
There was a silence as Harry digested this. How could Voldemort have made such a mistake? But even as he thought this, Hermione spoke, and her voice was icy.
“Of course, Voldemort would have considered the ways of house-elves far beneath his notice... It would never have occurred to him that they might have magic that he didn’t.”
“The house-elf’s highest law is his Master’s bidding,” intoned Kreacher. “Kreacher was told to come home, so Kreacher came home... ”
This passage seems to be hammering home the point that Kreacher was able to escape because Regulus had ordered him to come home. But wouldn't Kreacher have been able to escape anyway? Regulus's order did not create his ability to Apparate. So when Kreacher realized that he was being dragged underwater by Inferi he could have simply decided to Disapparate on his own to save his life. So why is it relevant that he was following his master's orders?
I understand that that's what the actual case was, but the passage seems to imply that he was only able to escape because he was following orders. But why should that be?