My reasoning behind writing that is because, in RO, he's jumping all over the corridor flinging his lightsaber around and force-slamming and choking everyone as if he just popped a ton of uppers. He's almost on par with Ren with what looks like a tantrum-induced rage...
ANH, which happens not-too-long after RO but long enough for Vader to catch his breath back, has Vader being calm, collected, being quite controlled in just force-choking one person, much slower with his lightsaber and in a more emotionally tight fight against Old Ben Kenner Toy Obi Wan Kenobi, and his voice sounds a bit different. And never once did the audience get the impression he had emotional issues of the sort Ren had.