[RightWhale]

the Japanese believed that their plan failed

I personally know one of the Japanese meteorologists who launched the incendiary weather balloons. They knew the success rate very well. Seki knew of at least one fire in Oregon that one of his balloons caused.

[Travis McGee]

The Japanes forest arson plan still at best (for them) would have only resulted in a lot of widely spread single point of origin fires, to be dealt with one at a time in the usual way.

This could not in any way compare to a coordinated linear attack on a single cloudless hot dry windy day.