A few photos of what I found when I did the vent switch tonight on my 2015 Classic.
Nearly all of the openings had the small tab. I used a pair of wire cutters and simply snipped it off. In the righthand photo from CraigT you can see the snap tabs and raised lip. Without removing the tab the lip can't fully seat.
To get the old covers off I used a couple small nail pry bars that I had. I wrapped the ends in a layer of electrical tape.
I used a finger to pull down on an edge, got the small bar inserted and levered the gap wider and then inserted the larger bar to further remove the grill. Once two of the four prongs were release I put the tools down and pulled it out by hand.
Only other thing to be aware of is that in some of the openings you can see the overlapping inner skin. I didn't find it a problem. Position the wide are between the plastic snaps so that they straddle the bit of inner panel that is intruding. All snapped into place, probably just enough give to allow the lip to full seat.
Total time about 40 minutes to do all 12. First ones with trepidation and the last few pretty quick