If that were true, then the Christmas tree fire would not have taken
out the entire house in only five minutes. A conventional circuit
breaker trips after the fire has started. This fire is why AFCIs are
now required for bedrooms - where an sleeping occupant has the least
warning time; where such a fire can be most fatal.

Huh? Unless there is something to limit the current, arcs tend to ramp up
in current demands.

Perhaps I am missing something here but I would be hard pressed to create an
"arc" between HOT and NEUTRAL (or ground) that would NOT trip a conventional
breaker. A "direct" arc would not have anything to limit the current.