Yeah, a quick look at my Club Nintendo history suggests that you're right: VC downloads seem to generally only count for the 10 coins if you do the post-play survey that appears a couple days after you get them. I suspect it's like this with all WiiWare and 3DS Download software too, you only get coins for doing their post-play surveys. Getting coins for just the purchase itself appears to only count for retail boxed games, or possibly for the digital versions of those same retail boxed games.