There's already dungeon experience mechanic in place for Chapter 1 which significantly eases material pickups for dungeons, with repeated runs eventually quadruple the amount of what you gather.
This new feature adds another aspect for the game for players who wants to collect more of a specific type of materials but want to spend their time gathering resources on another dungeon, or run the store instead. The gardening aspect is also entirely optional, and players can just ignore it if they wish to do so.