I can verify that the bridges are arched, cf. these quotes from TDR:

"The bridge was only the beginning. It arched straight to the walls that surrounded the island, high walls of gleaming white, silver-streaked stone whose tops looked down on the bridge's height." (TDR:107)

"[...] as she led Egwene and the others through the village to the great bridge, arching over half a mile or more of water like lace woven from stone." (TDR:106)

Anyway, had the bridge been entirely flat, it would still be ridiculous for Chubain to order a blockade to be set up outside the walls of TV. I wonder what the rationale for that move could possibly have been for the author? Also, this apparent lack of military insight makes me fear a bit for what the results will be of the presumably many battles that will be coming our way in ToM and AMoL... I know there is a huge demographic of WoT-readers with military connections, many of which have been in the same armed forces that Jordan served in. These people highly value Jordan's knowledgable take on battles and tactics. It seems to me that Sanderson's lack of experience and insight here might serve to give us incoherent/illogical battles, which would be a huge detriment for this series.

You are probably right, though, that it may be too much hassle for Sanderson to change these details at this point, as these basic misconceptions form the basis for much of the description for very many chapters in the book. I still hope that they will do it, however, as they apparently have been doing a lot of corrections in conjunction with the release of the digital versions of the books. And I certainly hope that they will take more time to eliminate erroneous details from Towers of Midnight, before that book is released. Otherwise, we will just have to keep brushing over these mistakes.