Parenting with Automatic Weights Only to Selected Bones

Right now when you want to restrict the influence of some bones only to specific parts of the model, the only thing you can do is to parent stuff to a specific bone with 100% influence using Set Parent To -> Bone. This is how it works: You select the objects in object mode, then shift select the armature, switch to Pose Mode, select a bone and hit Ctrl+P -> Bone. Now all the selected objects will receive 100% influence by that bone.

Assuming you have a slightly more complex scenario, you have several strands that are intersecting, each has several bones to be able to bend them. You want to avoid manual weight painting and parent the strands using automatic weights. You select the first strand, then you shift select the armature, switch to Pose Mode and hit Ctrl+P. You see the Set Parent To -> Armature Deform -> With Automatic Weights option available to you. You click on it. Then check the bones and realize it didn't only get parented to the selected bones, so it doesn't work as it should.

I found a workaround which does work but that work could be avoided if blender worked consistently. Here's how to do it:

1. Go to armature edit mode, select each strand's bone chains one by one and separate them into separate armature using P.
2. Parent each strand to its corresponding armature with automatic weights.
3. Join the armatures back with Ctrl+J.