What do shutter angles mean for electronic shutters?
It just refers to the shuttet speed and FPS.

As you probably know, 360° means the entire time, the frame is exposed.
0° means it is never exposed, 180° half of the time.

With digital shutters you can just take your FPS, for example 24, and calculate the corresponding value.

For 180°, you can double it 24*2=48 so youbget a shutter speed of 1/48s.
For 360° you can justvtake the FPS 24FPS = 1/24s.

The formula for any shutter angle being:

FPS / (Shutterangle / 360)
24 / (180 / 360) = 1/48