Have a vet find them if they are there and undeveloped, undescended etc. He is a"must neuter" dog for his health. All kinds of bad can happen if you don't. You might lose him early.
You are right. It is the same in the dog world. Cut off the blood supply to any organ inside the body and it can instantly become necrotic in a few hours,and death is emanate.I was thinking they would drop soon and not to over think it, but looking at the picture of your dogs groin, I think it's more likely he has retained testicles. My puppy is 19 weeks and both of his are very visible, and have been since he came home at 10 weeks old. They look like the other dogs, just not quite as big. I am a novice Doberman owner however, so wait for others with more experience to chime in before you worry.
I do know if he has retained testicles it may be best to neuter. Not sure what the timeline is, as far as when to neuter if they're retained. If not removed I believe it can lead to testicular torsion, that manifests as sudden abdominal pain and the retained testes can become cancerous. My knowledge on that is from horses, though, so wait to see what others say.