Yes, they do call the banks and the employers. There are plethora of cases filed in courts people challenging misrepresentations because of information retrieved over the phone. It cannot be spoofed either because sometimes they conduct parallel calls to you and your employer and have both of you quizzed about your work at the same time and then compare your answers to see if they match up or if you are making things up.This is pure BS. People at any bank would laugh loudly if the person on the other end of the line said 'this is IRCC calling, please give me your client information'.
No wonder people believe such non-sense if they have problem understanding simple cut-off score concept. I repeat: IRCC has no way to confirm their identity, when they're calling your employer, bank, or university. Such a call can be easily spoofed. So do they call? Answer yourself...
If you do not believe IRCC can verify your bank statement or if you must see this for yourself, go ahead and watch this clip from UK's border force show (remove the space): https:// youtu.be/BuOsUMNrpBY?t=18m12s