Bit confusing and appears to be missing information. "NON-chinese brand".... "NOT allowed". That's a double negative, so this really means that ONLY chinese branded phones are allowed?
The extension to this would be the assumption that you are IN CHINA, and therefore there is a push for local branded phones either for some kind of "support the Chinese economy" push, or national security reasons. Is this correct?
I would expect that the simplest way to enforce phone branding would be to physically check the labels on the devices. Even if they are not doing that NOW, they could in the future, and I would expect that you might get into some really big trouble if they do a random spot check and find that you're using a disallowed device.
My suggestion would be that you should fully comply with your workplace's requirements. Don't put any sensitive or personal information on your for-work phone, and use your personal phone when outside of work.