Yes that's true. To get my Google ID card I had to register online on a kiosk, you have to authorise a G+ app access to your account, if you do not have a G+ account you have to register.
Google HR use it for recruiting. I had to recommend a friend recently for a job at google. The whole job application process is done through G+, form filling, hangout for interviews, the works. Many google employees have secondary accounts that are not public but for internal use only, once my friend got past the first interview a new person circled them, a VP of HP then recommended him for the next stage.