I have a Nikon P520 camera and will soon be getting a mirrorless camera. I had sent a few Images for submission and it didn't pass the test. In the QC control guidelines, Alamy mentions that the only take photos from DSLRs and DSLR like cameras and not mobile phones. The P520 doesn't have a large sensor, but the images are shot at best possible image quality (ISO 80 and best JPEG quality) and have been my most successful images on Shutterstock and were accepted at istock getty. So they definitely don't lack in selling ability.
So does the P520 qualify as DSLR like?
I think they were rejected because of the camera eligibility.