Jeff
I don't see evidence of either. It looks more like the upper edge was trapped by the vent frame and the rest was just tucked in? Picture of the other side below;
Looks to me it appears to have some of the typical with age, brown sealant along that inner edge of the rain gutter and possibly the spray as shown on the other example (Reply #8) but the lighting and contrast is not as great as we would like. Did adjust it a little in the picture below. Since the sheet is plastic it appears this adhesive did not hold well over time. Of course the top edge didn't have to be held for long with the adhesive since one the trim and trim strip were installed the screws across the lip of the rain gutter would have held it up
The may have folded the upper lip over the rain gutters edge also.
