Le maître de céans de vient-il pas de nous donner sa bénédiction pour continuer en français ?!
Il faut bien sûr préférer 5...Db6 qui se voit accorder un point d'exclamation dans le livre de Johnsen/Kovacevic avec pour suite critique :
6.Db3
(6.Dc2 Fg4! Miles-Fressinet 6...Ff5!? 7.dxc5 Fxc2 8.cxb6 axb6 9.Ca3 Txa3 10.bxa3 e6 pas clair; 6.Ca3 a6! 7.Db3 Da5 8.dxc5 e6= une autre partie de Miles)
6...c4 7.Dc2
J'ai consacré une update à 7.Dxb6 axb6 8.Ca3. Le livre explique pourquoi ils préfèrent le retrait de la Dame :
"White to some extent threatens 9.Nb5, but Black has many ways to parry that. One may suspect that 8...Rxa3 and 9...e5 are not quite correct. ( Practice suggests the contrary on 8...Rxa3) It also seems likely that White may achieve something against 8...Na7 (Knaak's choice) and 9...Ne4. However, both 8...e6 (?! I suppose the author meant 8...Bf5 9.Nh4 Bd7 10.Nf3 e6) and 8...Ra5 (my main recommendation) have proved fully satisfactory in practice play. Play often becomes complicated with White trying to create confusion in the black camp with his minor pieces. However, even if White should succeed in picking up the b6-pawn, his knight and bishop often end up in danger of being trapped or shut out of play. We therefore will not go into any detail on this."7...Bf5(!) 8.Qc1 e6 9.Nbd2 Qd8 10.b3 b5 11.a4 a6 12.Be2 Be7
"White has not been able to prove anything here" based on Kharlov-Sadler Bern 96.
For me this is typically a dangerous equality for White, an easily obtained equality from where White can be outplayed by the opponent.
I prefer to be on that side of equality when I play the Prie for instance, or the Lemberger as Black against the BDG, for I completely agree with what you say, Arkhein, about its accepted version.
That is why the book advocates 5.Nd2 instead of 5.Nf3.
As for me, I see the radical Novelty 5.Qb3!? preventing Black's Queen's bishop to move out of the pawn chain as the only solution. Unfortunately the complications resulting from 1.d4 d5 2.Nf4 c5!? ( instead of 2...Nf6 3.e3 c5 4.c3 Nc6 5.Nd2) 3.e4! Nc6! are not much of my taste, so much to have dissuaded me from playing the London against 1...d5. But of course, if my opponent goes 2.Nf3 e6, I willingly play 3.Bf4 and not 3.a3!
To loop the loop with that order of move, 3...c5 4.c3 Nc6 5.e3 transposing in your 5...e6 instead 5...Qb6(!) only aims at neutralizing the London bishop at the price of shuting in the queen bishop.
Then 6.Nbd2 Bd6 7.Bxd6 Qxd6, transposing into well known positions with the reversed colours, is just fine for White because it shall not be so easy for Black to liberate his play with a further e6-e5. Either after 8.Bb5 or 8.a3 ( exactly Bacrot-Svildler Linares 2006 with the reversed colour and an extra-tempo for White) intending b2-b4 or a combination of both; to finish on an ironical touch about the most innocent movement of the White's a-pawn