However, aren't so-called "limited editions" identified as such by being numbered?
Not always. A true limited edition will be (and they are usually restricted to about 10,000 copies) but sometimes they'll be given a longer run but one that will eventually be superceded by a standard pressing. The 2CD version of Heathen, for example, is becoming somewhat harder to find and will, eventually, be almost impossible to buy new. However, the standard edition will be around for many more years to come.