It's not aimed at pvp at all. It has to do with the promotion for the warcraft movie, where a lot of the theaters are giving a free month of wow to new subscribers. They're expecting a bunch of people to try wow for the first time in the next couple months.
But the leveling experience pretty much sucks terribly because they've spent ten years screwing with xp, damage scaling, and spell/talent order. Those changes have always been aimed at max-level PvP or PvE, with no concern paid to the effects of their changes on leveling. As such, the leveling process is basically boring and broken af with heirloom heroes two-shotting mobs, classes missing core abilities (spriests from 10-24, for example), players outleveling zones before they're halfway through, lowbie dungeons leveling you up 3 times in 15 minutes, and so on. The changes to melee scaling are just a part of a larger set of changes that also messes with xp and world mob health. It's all just a last-second attempt at damage control toward the worst problems in the leveling process right before the movie brings a big surge of new players, so they don't just have a terrible first impression and quit immediately.
Of course these changes it will totally still affect lowbie pvp, but none of it was designed with twinks in mind at all. Which of course is the attitude that created this mess in the first place. Assuming this is a twink-related nerf just makes the mistake of thinking Blizzard even pays attention to us.
Sidenote - What they should have done was kept like a third of the Cataclysm revamp team around as a permanent fixture, fixing a zone or two every patch and keeping an eye on the leveling process as things go. But that would involve spending money on something other than max-level content, which is not something Blizzard has shown any willingness to do.
