It doesn't allow you to stay permanently, but it does allow you to change your mind and apply permanently.
This is unlike other temporary visas, that specifically say that you have to return. If you break that promise, they may not let you in again on a temporary visa.
This distinction is a huge deal if you want to get a visa into US. To get temporary visa, you have to have some reason to return. Education, relatives, business, work, property etc. If you are an unemployed young person, you are not getting a visa. If you are in the last year of school, it's a high probability too (YMMV of course).
So... you failed to mention that you can in fact apply for green card just after being on H1-B for 6 years. You don't have to be in a special category. 5 more years to get a citizenship. From entering USA as H1-B worker to becoming a citizen you need a minimum of 11 years.