I have been in San Francisco for a week, and saw the Ansel Adams exhibit of 100 of his prints both on the first day of my visit and the last day of my visit. Some of the prints were contact prints and some were enlargements. Unfortunately, I did not have my tape measurre with me so I could not calculate the aspect ratios of the prints to determine if he composed on the ground glass or on the easel. Of course, as someone noted above, for his enlargements, he could have cropped to the same aspect ratio as the ground glass, and we would never know. I may go over to the library when I get back home and measure up some of AA's photographs to satisfy my curiosity.
I also saw an exhibit of Robert Misrach's photographs down at the Fraenkel Gallery. His working method is using an 8x10 view camera and printing full frame. The aspect ratio of his prints was a smidge off because he prints a sliver of the film rebate on one side bearing the Kodak emulsion number. I haven't seen all of his photographs, but of the ones I have seen, they are all in landscape orientation, which may indicate another of his working methods. Misrach's photographs at the Frankel Gallery were printed 62-3/4 x 82-3/4 and were so stunning as to be awe-inspiring.* Four of Misrach's photographs also appeared in the AA exhibit but in a much smaller print size, and were only okay. The ones in the AA exhibit were printed in 2016 if I recall correctly, and the ones in the Fraenkel Gallery were printed in 2023. The large ones were luminous and leapt off the wall. The small ones sat on the wall starving for better illumination.
I offer these examples solely as observations. I do not mean to say that composing on the ground glass is the "correct" way, or that my photographs are better than yours because my working method is to compose in the viewfinder and on the ground glass. I am just telling you what I saw. I also saw photographs of several photographers at the the SFMOMA and the Robert Koch Gallery, some of which were cropped and some of which were full frame (or cropped to the same aspect ratio as the camera used). You don't want to make a hasty generalization about a photographer's working methods based on just one of his photographs.
*While I do not know for certain, I think for the large prints at the Fraenkel Gallery, Misrach's 8x10 negatives were copied using a Phase One XF camera and IQ4 150MP color back rather than scanned. The level of detail was astounding. Misrach's prints both at the AA exhibit and at the Fraenkel Gallery were pigment prints. Once you have seen them, you will retire "stinkjet" from your vocabulary forever.