Aye, there have been considerable changes to the gather system since 4.8. The problem should be resolved fully in 4.9.
ShouldGatherBlueprintPinNames has been replaced with ShouldGatherFromEditorOnlyData, which will cause any properties marked as editor only (conditionally compiled using the WITH_EDITORONLY_DATA macro) to be gathered if true - otherwise, they are not gathered.
Thanks for providing an additional workaround in the meantime. There are a number of additional sources that might be gathered when not desired, sans the new changes for 4.9.