Ignition has always exported only properties that differ from that property's default value. Otherwise, exports would be bloated by the many dozens of properties that aren't always used.
If you want to obtain the defaults for properties, there are java SDK interfaces that will help you, but do not have formal system.* jython APIs. The set of possible properties varies with installed modules, and can vary by tag provider. If you'd like to explore the possibilities, my latest Exchange resource enumerates them for use in the Perspective implementation of the Tag Report Tool:
Look at the library function exchange.tagReportUtility.providers.getProviderProperties(...) for the technique required.