Click and drag selecting will select anything that has a part of it inside the selected area.
This makes it hard to pick things that are also close to other things without also picking them....
In other software I have seen various techniques to overcome this.
- If you want only one select method make it select things completely inside the area - that's more normal
- Make it a setting to choose which method it uses
- Use a modifier key to switch
- Dragging selects everything fully contained unless you drag from bottom right to top left (sketchup does this it's very easy to use)
I will also post a feature request. I ask here in case there's something I am missing.