Could you expand on that statement a little?
Where the above PDF lead to the 3 PDFs I've attached below.
Lowering the magnetic trip value on single pole US breakers worked well, until it was theorized that in long circuit runs with a high Ze short circuit currents in US home wiring could be as low as 75 amps at the furthest point in the run.
A concept breaker was designed with a 75 amp pick-up, but was soon realized this would cause nuisance tripping on high inrush loads like vacuum cleaners, tools, ballasts, window AC units and light bulbs burning out.
As such an electronic AFCI was created in an effort to discriminate between inrush and sputtering short circuit aka arcing faults.
Easy solution would have been to restrict the length of 2.08, 3.31 and 5.261mm2 circuits. But nope, never happened.
Here is the whole concept being demonstrated:
When current is just below the magnetic trip level on a EU breakers it takes 7 seconds to trip. When set above the magnetic trip level that opening is instant.
The theory is that 7 seconds vs 1.5 cycles is the difference between a house fire.
The theory also stretches to cords, in the UK plug top fuses blow much faster than a breaker when the cord is damaged.