The Pixel 3 XL will not have a dual-lens camera on the back, as a series of leaked images have shown, and the prototype device in these images seems to be the only true thing. Although most Android flagships have a double-lens shooter on the back in 2018 – one of them has three cameras – Google seems to be just stuck on one.
Google has manufactured 9to5Google's Pixel 3 prototypes with two back cameras Stephen Hall, but ultimately chose to go with single back cams:
The same 9to5Google found evidence that the mysterious logo on the back of the leaked Pixel 3 prototype was from Google :
So it seems unlikely that the leaked images are fake. As we approach the Google Pixel 3 press conference, we see even more leaks, including the actual photos of the new Pixel 3 phones.
Google claimed last year that the Pixel 2 does not require a dual camera and these algorithms can replace a secondary lens when it comes to creating cool portrait images with depth of field effects. 
The company continued to boast that the Pixel 2 camera scores 98 points on DxOMark's meaningless scoring system, which was the highest score at that time, and the iPhone X exceeded by one point. In the discussions, however, the dual-camera setup of the iPhone X won the portrait battle
fast-forward to date, and any phone that scored better in the DxOMark's leaderboards than the Pixel 2 has at least two cameras on the back, the top phone grabs three of them. Of course, these phones have all been released after the Pixel 2 and Pixel 2 XL, so it's quite possible – probably even that Pixel 3 will skip the competition once more when it's released later this year.
It will be interesting to see if Google mentions DxOMark points on stage during the Pixel 3 event this year whether a single-camera setup is enough to keep the Pixel 3 on par with its rivals.