Being quiet about upcoming GPUs is not a smart move anyways. Lots of lost sales, as AMD has seen for the past few months. Nothing to see here IMHO.
Hopefully the performance is good though.
Honestly, the same average joes that don't follow reviews of after-market cards, post-launch reviews and are brand attached, are the same ones who wouldn't read a technical forum such as ours to even learn about these leaks. I think someone who does follow the GPU industry closely has either already purchased a 970/980/Titan X or a heavily discounted 290 card, or is waiting for the new cards. Your typical BestBuy PC buyer is the type of chap who would be buying a 980 on June 16th because "he heard NV is the best / has class leading features and perf/watt" even if R9 390X beat the GTX980 by 30%. The average PC gamer doesn't follow the market like we do. Leaking performance data actually hurts AMD more because NV could devise a cost-cutting / GPU refreshing strategy that undermines the entire launch. Also, if someone knew that a $299-349 AMD card was as fast as a 290X but used 40% less power, had HDMI 2.0, revised UVD, etc. they might not want to buy an R9 290X for $280-300 and AMD would be left with a lot of unsold inventory.
Remember how 680 barely undercut 7970 by $50 and the entire momentum of 7970 was destroyed overnight. If NV had all the key data 2-3 months before launch of R9 300 series, they could take the wind out of AMD's sails. It's probably why we have rumours of GM200 6GB card coming soon because NV wants to purposely clamp down on the hype behind R9 390 series.

Remember how NV was rumoured to have
120,000 unsold GTX570 cards which forced them to delay the GTX660 by 2-3 months? Would it have been better for NV to leak 660 specs? I doubt it.
The last time AMD almost executed with R9 290/290X. Price/perf was top notch. They just couldn't meet supply and their reference cooler launch strategy was an big mistake. However, if on day 1 we had a card like Sapphire Tri-X 290 for $399, and reviews were based on it, and the supply was not adversely affected by mining demand, I think 290/290X would have hit it out of the park back then. This time AMD has the chance to correct many of these mistakes.
In this case the choice of Card A vs. Card B doesn't tell us enough though. 980 can be the +$350 option and be faster than the 380 and be HP's higher-end offering and 380 could be the +$200 option.