This comment is usually made in respect of comparing the passports of different countries in order to grade them or to try to remotely identify them. Practically all e-passports conform to the ICAO standard Doc 9303 (ICAO refers to International Civil Aviation Organization, an organization of the United Nations which contributes to the regulation of international civil aviation). They also implement a set of the minimum security standards. While there are small differences between the e-passports of different countries, they have overwhelmingly more in common than not. E-passports are issued by one country to its citizens, and have to be read by all the other countries to which they travel. To achieve this level of global interoperability, all e-passports must conform to Doc 9303 in all essential respects, so the amount of variation is minor.
Courtesy the Keesing Journal, 2009