Think you meant to say "longer eye radius on the A3." But a longer sight radius is never a disadvantage in terms of accurate aiming. Chief disadvantage of the M1905 was its placement too far down the barrel, because it was supposed to be a compromise between an open sight, which some Army troglodytes wanted to retain, & a peep sight, which must be close to the eye for max effectiveness. It's deficiencies were quickly recognized by the leading rifle experts (such as Crossman, Whelen, Hatcher), but they didn't sit on the Ordnance Board that approved it. The same Buffington who authorized the trap-door sight in 1884 was Chief of Ordnance until late Nov. of 1901, which suggests that the resemblance between the two sights was not accidental.
I was referring to the placement of the sight on the 03 and it’s distance from the shooter being a disadvantage. I once bought a “long eye relief” scope for a Mauser that was designed to be placed several inches away from the eye and somehow my mind shifted into neutral and confused “radius” and “relief.”