Those answers seem wrong.
Think of a finger – in most rigs it has a bone depth of 3 bones from the knuckles (or 4 if you start at the wrist)
so if you put bone name “ringfinger”, with bone depth of 3, all the joints for that finger will be considered, assuming they are nested properly
Bone depth isn’t a control of weighting or distribution for the node’s various input poses. That’s what Blend Weights do. Depth is a numerical way to count down a rig’s joint nesting. For example, your palm bone may have several nested bones at depth1 (knuckles). It is included as an efficiency measure so you don’t have to create a larger array of per bone entries than you really need to.
Setting a bone depth of -1 might well disable a blend pose because you’re clamping what can be affected to nothing, but that’s a side effect.
If I’m wrong I’d like to know.