Right, there are also different standards of Hepa. One that is not as good that the chinese companies are using. The other standard is used by european and US companies. Also by Coway from Korea I believe. I don´t remember the details but they can be found on internet. The simple rule is don´t buy the cheapest and not from China. I believe the chinese brands Hepa is Hepa 10 or 11. Not more than that.
My old vacuum cleaner is Hepa 14. Just because it says Hepa it don´t mean anything magic. It depends on WHAT hepa it is.