Could it be that 8...exd5 is not in fact the most common move, but it looks that way because the database program catches the transposition? This transposes to one of the main lines usually reached from 7.cxd5 exd5, which has been very popular on GM level in recent years – it's no longer thought to be an easy += for White.

I know Chessbase does this kind of transposition search in its various tree and book features, and sometimes this can mislead people into overlooking inaccurate move orders.

It's also possible many Black players were prepared to play this main line anyway (via 7.cxd5) and just accepted the transposition instead of trying to refute a rarer move order that they might not remember much about.

Looking through the database I'm fairly surprised that 8... exd5 is the most common move. It seems to me that white gets a fairly comfortable game, no advantage though I suppose, if they play accurately. What really drew my attention was 8... Nxd5. What is white's best try here?

I've been looking at 9. Bd2 and if 9... Nc6 intending e5 the best I could see was 10. f4 (no games in the database) a non-typical position, with quite a few tries such as 10... f6, 10... Qh4+, 10... b6, and a few others.

if 9... b6 10. Bd3 Ba6 11. Bxa6 Nxa6 I think it's a fairly even game, white just develops normally then plays e4 after Rc1 to grab the center and kick blacks knight, and afterwards repositions his bishop to e3. I don't think whites position is uncomfortable.

Not a ton of games in the database for this line from what I've seen, making it hard to judge. Anyone have thoughts regarding this?