That's actually a myth. Obviously these particular photos are staged, but the whole "if a photo comes from Backgrid it means it was staged and sold by the celeb" thing isn't true at all (and iirc originated on Tumblr in the 'skeptic' communities, which are basically groups for fans to get together and talk about how much they hate the wife or girlfriend of their favourite male celeb, like Georgia Tennant or Sophie Cumberbatch- a really common theme in the fandom for any popular male actor is the idea that his wife or girlfriend is just using him for fame, ergo any pap photos were staged by the woman).
I work in the media/entertainment and have sporadic dealings with Backgrid, they are one of the largest celeb photo agencies out there, and buy photos from thousands of photographers worldwide. Yes, celebs certainly do work with paps (though usually that involves celebs tipping off the paps as to their location, celebs actively being involved with selling the photos is less common) but Backgrid is kind of the automatic first stop for any freelance pap with celeb photos to sell.
If you look at Backgrid, they have plenty of photos for sale taken on red carpets for celebrity events, where the pap photographed every celeb who attended that event and walked the red carpet. So pretty obviously not a case where each individual celeb on that red carpet called up Backgrid to sell photos of themselves. I had a look just now and the most recent photos on Backgrid are the Rolling Stones at a press call (photographers from every agency present); Elon Musk; and Jennifer Lopez. Jennifer Lopez possibly might be calling the paps for attention, but does anyone really think a celeb of that level is actively selling photos of herself online to make a few thousand dollars?
The idea that you can tell if a photo is staged based on whether it's on Backgrid or not is just one of those weird Internet myths created by terminally online fandom people who don't work in or know anything about the industry. The reality is, it depends on the situation, and you can't always tell. Plenty of photos on Backgrid are not staged, and plenty of photos on other photos agencies like Getty Images, Wire Image, or Rex Features are staged.