Sadly you are partly right.
HR is who writes the requirements, selects who will get through to be interviewed and they rarely have any idea what the actual requirements of the job are.
The department managers usually have little or no say as to who they will be interviewing.
Once had a case where they had a temp that had been in the job for a few months and was doing great. The boss told her to apply for the job. Her CV never hit his desk so he assumed that she didn't want the job. So he went with another candidate. On her last day he told her that he was sorry to see her go and she asked, "then why didn't you at least interview me?"
HR had decided that she "was not a good fit" because she did not have a degree and had put her application in file 13. She had been doing the job just fine without one. But they knew better.
The HR department is root of all evil at times.
My current position I was already hired for by my previous employer from another company. He said all I had to do was contact the HR dept. and get the paperwork done.
The gal called me every day because she couldn't understand why I wasn't selling my home to relocate to the office out of state.
She couldn't wrap her head around the fact that only an idiot would sell their residence, purchase a new residence for a “Start-Up.” LOL. Then to your point. You have to spend hours and days explaing your resume to them. Just forward it to the dept. manager.