This is a genuine question. There's probably an explanation for this I haven't thought of, but it just occurred to me and I thought I'd post it here. I'm sure a central reason would be that Japan was going to surrender, while Germany wasn't at the time.
There were war crimes committed against Germany and they were bad. Killing civilians doesn't do shit because fascists don't care about their own civilians. It's just kinda sus if someone is overly concerned with those specific instances.
Yeah it's definitely used as an anticommunist dogwhistle a lot