I’ll play devils advocate.
Your private life is all good and all until it interfiers or effects your work.
If your private life had no effect to what kind of candidate you were than yeah this is ridiculous.
But since we all know and had examples where private life directly effected your work and your productivity its fair game to find out as much about you as a candidate as possible and this is no worse than making you take a drug test as that affects you, your credit score in certain companies, interview questions etc. They want the best candidate who’s applying to work for them.
For all we know they won’t even check your account and it’s a dummy test. If you have nothing to hide many will give their accounts. (yes I know that many that have nothing to hide will object to this as well, but those with a “sketchy” account definitely will object.