I've (literally) employed people who were working 3 jobs without any of the other employers knowing about one another. We were being scammed. This happened not just once, but with 2 people (1 full stack engineer who is a HN regular, and another was an account manager).
This was at a 15 person company, and 2 out of the 15 were working multiple full-time W-2 jobs all with full time benefits. At the end they were both let go once we discovered the deception (their downfall was neither of them were meeting productivity expectations, not getting their work done)
After this, we heavily beefed up our pre-employment screening, which is all of what this person is complaining about.
Unfortunately there are people in the job market who scam companies. To find and weed these people out before they make it in the door, we need to do things like verify your degree (even if it was 20 years ago) not because we care whether you have a degree, but as a test to see if you were truthful on your resume.
Edit: Also, if anyone requests reference checks from your current employer, you should say no. It's not standard practice to check current employer, only prior employers (at least in the US).