The drop rate for flint is balanced around 1-shotting rocks.
I regularly go mining and come back with 300+ flint, all from just max luck and smashin’ rocks.
In a few levels with max mining skills you’ll be bringin’ back 3,000 rocks after a mining trip and that’s a TON of flint.
You don’t need THAT much flint in the early stages either I’d say.
That said, they could update the game guide to explain that some more, or encourage people to explore biomes more. I believe you when you say you landed in an area with no flint, it must have sucked.