A first-use observation from desktop Chrome: starting a default 60x60m project and using Raise produced a clear raised area. The terrain stayed green until clicking Generate Biome, which then added distinct rocky cliff coloring. Real Time was off initially.
A small hint near the sculpt controls, such as "Enable Real Time for automatic biome colors, or click Generate Biome to refresh," would help connect that setting to the after-every-stroke behavior described here. With the biome panel scrolled to the top, the manual button was below the visible part of the panel.
This was a browser sculpt-and-biome check; GLB export and engine import weren't tested.