And my guess is that OA isn't reliable around high strung wires/cables, thin branches, or bodies of water?
No need to guess.
The OA system is good, but not magic.
There are several situations that it might have difficulty with.
This is from p. 57 of the
Air 3 manual.
Note the last point.
The vision systems cannot work properly near surfaces without clear pattern variations or where the light is too weak or too strong.
The vision systems cannot work properly in the following situations:
a. Flying near monochrome surfaces (e.g., pure black, white, red, or green).
b. Flying near highly reflective surfaces.
c. Flying near water or transparent surfaces.
d. Flying near moving surfaces or objects.
e. Flying in an area with frequent and drastic lighting changes.
f. Flying near extremely dark (< 10 lux) or bright (> 40,000 lux) surfaces.
g. Flying near surfaces that strongly reflect or absorb infrared waves (e.g., mirrors).
h. Flying near surfaces without clear patterns or textures.
i. Flying near surfaces with repeating identical patterns or textures (e.g., tiles with the same design).
j. Flying near obstacles with small surface areas (e.g., tree branches and power lines).