I'm sure the CG was glad to know someone was telling them they were "practicing" before actually doing it.
I have fired old 12GA marine flares on land and yes, I have had to run and put out the resulting grass fire. It seems they are often still burning when they hit the ground.
I used to live adjacent to a rice field which was flooded annually and miles from any navigable body of water. I never had a single grass fire result when I fired flares over a flooded rice field.