Angle of view is the most accurate way for comparing lenses and formats. The Focal Length Equivalent Chart is to aid us with a very simple comparison to a format that 99% of us have graduated from. The 35mm comparisons are very close. The angle of view was measured from the actual exposed aria of the negative whenever possible. This is why a 6x12 and a 4x5 have the same position. (120mm is the actual exposed with of a Fidelity cut film holder)
Please note that while a lens may cover the horizontal angle of view given in the chart, coverage is necessary for the diagonal angle of view. These charts are intended to aid in lens focal length selections. The coverage of the lens and the movements available with any given lens is an entirely different matter that I hope to address in the future.
Thanks for looking.