In the first game I played today (medium map size) some ressources didnt spawn at all:
no berries
no clay deposits
no greens
I explored the whole map, and because of missing clay I couldnt proceed in the game, get healer, build buildings, ecc.
The second game I started (small map size) those ressources did spawn in.
Depending on the map you generate, that is absolutely possible, yes.
Some maps completely lack certain resources, for which you may end up needing to trade, but they have an abundance of others in return. Sometimes you need to explore to find resources (the initially revealed area at the start of the game is only a small fraction of the full map)