Jesus...My bad I was too excited when writing the notation.
11.a4 a6 In the line following it every number is one too low. 12.Nc4 etc. No further excuses on my part, that was just a rushed post, weak stuff
The point I was getting to wasn't equally rushed though, and to elaborate a bit on why I found it so exciting: Usually black has been in fear of Nc4->Bf4 hammering the d6 square and has thus plaid either Re8->b6 or b6 to enable Ba6->Bxc4. If black can place the pawn on b5 or provoke a5, that changes things.
I did analyze other continuations as well:
12.a5 Nb5 This is what I'd expect to see most besides Nc4.
13.f3 Nd7 Black is setting up for Nc3->Bxc3 and white can't really do that much to prevent it besides:
14.Bxb5 axb5 15.Nxb5 b6 Not just to capture on a5 but to continue with the ambitious Ba6->b5.
16.Nc4 Ba6 17.Qa4 bxa5 18.Nbxd6 Nb6 19.Qc2 f5 Is apparently the best play, with too many tactical details for a post, around +0.2 so very good indeed.
13.Re1 Bd7 14.Bf3 Rb8 15.Nc4 Nxc3 16.bxc3 Bb5 17.Nxd6 Qxd6 18.e5 Qd8 19.Bg5 h6 20.exf6 hxg5 21.fxg7 Kxg7 A forceful and very messy line +0.3.
12.f3 Rb8 13.a5 Bd7 This is most likely the critical line, I'll post more on it later. I think disposing of the bishop with Bb5->Bxc4 is more principled and active than 12...b6 slowplaying for b5 or 13...Nd7, but will have to do some more concrete analysis to make a better judgment.
About the Bxa6 line:
I should've mentioned that 10...bxa6 11.Rc1 Is VERY important. Enabling b3 as a response to Rb8, otherwise black can easily activity their way around the structural issues.
[EDIT: black also has the interesting option 9...Re8 to wait out Be2 or Bd3 before playing Na6]
I'd agree with your response to said clubmate, I'd go as far as to say it's a line where you have to actively disrespect conventional rules of structure to find the necessary dynamics.