This is a specific OO2 issue: when a document is saved in OO1 format, the list objects are arbitrarily saved as 'text:ordered-list' XML elements. But each one is saved with an appropriate style, in order to be displayed with or without numbers.
The OO1-compatible XML, when generated by OO2, is not exactly the same as the native OO1 XML. One could regard that as an issue, but it's a transitional issue only. Hopefully, we will have to deal with only one open format soon.