Electure,
Of note, the old "Carpenter's Rule" for blocking = 3 from a corner, and 2 from an opening. These were put in to give the wall rigidity, not as fire stops.
Yes quite true.
To a degree, these pieces of timber are designed to be used to fasten plasterboard (Sheet-rock) linings to.
These timber pieces are called noggings in the UK and over here in NZ they are called dwangs.
By convention, plasterboard sheets are supposed to be laid horizontally across a wall surface, not in the more commonly-seen vertical orientation.
This is the reason that the timbers are staggered, to provide nailing timbers for both top and bottom sheets on the wall.