Heres two maps. First is a modern map of the Aachen area. Note the Hurtgen Forrest to the SE of Aachen. Advancing into the forrest flanks Aachen. Securing the forrest keeps enemy artillery and flanking attacks off a future advance out of Aachen along the major roads to the NE.
Next is a map of the Hurtgen Forrest. This shows the front for 2 November when the battle in question nominally started. Note however over half the forested region, to the SW, had already been capture in the preceding weeks. Also that this is where the fortified West Wall had been breeched. Finally note how this front line of 2 Nov flanks Aachen to the NW.
I still have a lot of questions, but can see some logic in the attack. It may be the intent was to flank the relatively well defended West Wall to the south out of the terrain shown on the Hurtgen Forrest map. A longer view might be securing the entire Hurtgen Forrest out flanks the Aachen area. That may not hold up with more information, but on the surface both look logical. Many sources cite observers who described the 1st Army staff variously as 'worn out, pedantic, unimaginative, hostile. The 1st Army commander was also described as tired & unenergetic during these autum months. Col Dickenson the 1st Army G2 rejected assistance from the OSS, directing the OSS liaison team to leave his area. Devers, Patch, Patton, Simpson, and Bradly all made use of the OSS, integrating the liaison teams into their G2 operations, and utilizing OSS missions in their sectors. If Col Dickensons G2 was as dysfunctional as all this & other evidence suggests to German defense in the Hurtgen may have been a surprise. Col Dickenson was certainly surprised five weeks later by the Ardennes offensive.
One other point. Bradley at least twice, once in Tunisia, and once in Sicily, broke a German defense line swiftly by making the primary attack of his II Corps through rugged uplands, which were in each case less well defended. It may be when he saw the plans for this offensive forwarded from 1st Army he saw it as what he might have done, & not considered a stronger German defense.