This is a neat idea, but the math here seems heavily rounded in somewhat weird ways, so it seems like they are vastly overselling the capabilities for the current models at least.
They say 100,000 trees a day based on being able to fire 1 seed per second, but there are only 86.400 seconds in a day, so that's rounded up. Still, their 1 billion number based on 60 'teams' should land them closer to 2 Billion with that number than 1 billion they are claiming. That may be good that they are rounding that one down to be realistic though, as these are "germinated seeds" they are shooting, not saplings or larger, so there is likely to be decently less that make it to a reasonable tree stage than are planted. The number also relies on being able to work around the clock all year long, and doesn't seem to account for the refill and transport times which may be big factors since they claim currently each drone can only carry 150 'seed pods' at a time. Since these are still operated by humans (they mention a pair of operators for each 'team'), I'm doubting they would work around the clock anyway.
That all said, it sounds like this would go a long way towards improving the planting situation and speeding things up at least somewhat. If successful, I could imagine larger teams of more than 60 drones in operation, and perhaps investment into improvements such as larger seed pods, faster drones, or more automation for planting to reduce operators.
If only drones existed 30 years ago!