Each write to a memory location wears out that location slightly degrading it's oxide layer. Flash memories compensate for this by "wear-leveling" which spreads the writes around to different locations to make sure the device wears out evenly.
It will mark bad locations and stop using them. If you run with the device almost full then it cannot effectively wear level and the few open locations will be overused and wear out.
It's not specifically small writes, it's the number of writes to any one location. But of course it's faster to do small writes so you end up with more if they are all small.
Also, there are flash memories optimized for performance that will wear out faster and others that are optimized for longevity that write slower.
Keeping the device cool will extend it's life also.
For longest life, keep the device cool and mostly empty and minimize writes. In critical applications find a device that optimizes lifetime over performance.
So either incomprehensibly incompetent or unimaginably evil. You can pick one, or acknowledge both.