It occurred to me, last year Red Bull had an upright guide vane at the edge of the bargeboard, which combined with the bargeboard created a sort of tunnel. Mercedes, and now McLaren have tried exploiting this area, this year Red Bull instead have gone with a different arrangement, using the two little horizontal winglets to channel air instead of an upright. I suppose that the channel is difficult to achieve with the rest of side pod end fences.
Last year this vertical end fence was at the edge and tip of the bargeboards, and used the trailing slope of the bargeboard to create a sort of tunnel.
If this area has been deemed to work better with those little wings instead of the vane tunnel, who am I to judge. However that area has changed and not sure it changed for the better.