Extremely small microbiome

I stumbled apon this microbiome, I'm awear that there are many instances of these but one is far odder, a 1 x 2 block dark oak forest biome that A) has managed to spawn a 2x2 tree despite being half in a birch forest and  B) doesn't have the correct dark oak forest grass colour and has maintained the birch forest colour (biome blend is off)