It's quite possible the behaviour is because the grouped objects had that wrap format before they were grouped.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]

No, unfortunately. This happens every time I group or ungroup objects, regardless of wrapping style they had before. So a typical action for me is (if I have to change something in a grouped image for example) ungroup, right click (as all items are still selected after the ungroup action), set wrapping style to "top and bottom" (because it changed back to "in front of text"), do the modifications I need to do, regroup, set wrapping style to "top and bottom" (again, because it changed back to "in front of text").

I have done a little testing, and what I have found is the following: All objects (text boxes, rectangles, arrows etc., the kind of objects I normally use when making figures) have wrapping style "in front of text" when created, regardless of the default wrapping style. Even if my first action when creating an object is to change the wrapping style, it changes back to "in front of text" every time I group or regroup. Seems like this is some type of default behaviour that I at least haven't found a way to override...