Yes, this was an oversight and , yes, this can be fixed. All reports and fields can be edited by selecting a report and selecting the Reports -> Edit Reports menu item (or by double-clicking on a report or field).
To fix this particular problem, do the following steps:
- Make sure you are using version 3.3 or higher of Statbook
- Select the report which has the AVG or OBP field
- Double-click this field (not the report)
- With the field selected (e.g. AVG), from the 'Favorites' list, select the appropriate item (e.g. Average).
- Repeat steps 2-4 for each field (and report) which needs updating