It is standard practice to estimate instrument readings from the faint indentations left in the dial face at the moment of impact. The wing contact with the railroad embankment was unlikely to have been severe enough to produce such a mark. We are left to conclude that the second impact with the ground that detatched the nose section was the one that produced the witness marks used to estimate the aircraft attitude at that point.
It is very tempting to try and read between the lines and second guess the investigators, especially when an element of doubt has been raised about certain aspects of the report. I prefer to believe the report should be read without trying to put a modern interpretation on the wording. It is clear the investigators at the time knew what they were doing.
What I find incredible is the accuracy with which cables in the control runs were expected to be assembled and installed. Cable runs of hundreds of inches were expected to terminated and fastened to tolerances measured in hundredths of an inch or better than one part in ten thousand. The aircraft was originally built with the precision of a Swiss watch, an incredible technological achievement. Despite the disruption, the investigators were still able to draw meaningful conclusions from the wreckage.