Per the link cited at GlobalSecurity?.org, the leaflets were designated as propaganda by the military in Japan. It appears that the contents of the leaflets was correct. The leaflets read in part Read this carefully as it may save your life or the life of a relative or friend. In the next few days, some or all of the cities named on the reverse side will be destroyed by American bombs. ... We cannot promise that only these cities will be among those attacked but some or all of them will be, so heed this warning and evacuate these cities immediately. (rest of text at bottom of link cited above.)

0. The leaflets list a set of 35 cities that may be bombed.
1. The leaflets do not mention a new weapon.
2. Japan had been subjected to firebombing for a extended period. It appears that the contents of the leaflets are not inconsistent with continued firebombing.
3. Civilian evacuation would serve to decrease the number of civilian casualties.
4. Would it have been a morally superior act not to have dropped the leaflets.

Are these leaflets propaganda ?
Should these be described as propaganda leaflets ?

Please note: the question of whether or not the atomic bombs should have or should not have been used against the cities is not the subject here. That's quite a different question.