This is the most reasonable interpretation, in my opinion.I also do everything based not on the lighting conditions of what the observer is standing in... I do it based on what the object or person being perceived is standing in.
- If the target is in bright light, any perception checks made to notice details are made normally.
- If the target is in dim light, any perception checks to notice details are made with disadvantage.
- If the target is in darkness, you cannot make any perception checks to notice details, and in fact cannot see the target at all.
If you have darkvision, move each result up one line. Perception checks to notice details on targets in bright light and dim light are made normally, perception checks on targets in darkness are made with disadvantage.
I treat the darkness spell not as though the area is just regular darkness, but rather that it is a sphere of what you might essentially consider black ink. It would be considered a "solid" object as far as light sources are concerned (whether within the sphere or behind the sphere). A light source brought into a darkness sphere disappears (and does not radiate any light out to any radius), and likewise a light source that goes behind the sphere also disappears, although the radius of light it projects might be noticed if it is wider than the sphere of darkness. Most of the time it does, and you'll probably have a zone of dim light haloing around the darkness sphere that the perceiver can notice.