In high school, I took advanced level world history. Then the teacher specified and said we were learning Western history. I was excited, curious as to when we'd learn the other part of history. The school year ended and the only time we talked about not-western history was when we learned the world religions.
I was disappointed. "Why is it called world history when we explicitly left out half of the world?".
I'm in the USA, btw. So why is there so much emphasis on western civ in world history classes? Everything I know about Asian and African history came from traveling and random moments of learning in my life. I know even less about Oceania. I feel embarrassed.
This is a question to direct to your teacher. Without knowing them one can only speculate. Often when people drop the rest of the world from a world history course it's out of discomfort with history they don't really know- or that they themselves never learned. This can especially be true of older teachers- but plenty of younger ones too can manage to entirely avoid doing any world history courses at college/university if they were maybe just more interested in American history or something else. Often if a teacher hasn't been exposed to a topic, they might not feel comfortable teaching it or they might just not find it interesting as they don't really know it, or they might not see value in it. It's hard to say really- impossible to say actually.
So I would ask them. That's the only way to know or get an inkling for their reasoning.
It's good your curious. Hopefully you'll have future opportunities to discover more about actual World History.