Yet the Italian police have no issues with an elderly Fiat 500 taking up the same width of tarmac and wobbling along likely more slowly than pro cyclist on a training jaunt.
As a technical point of order, it's safer if the outside rider isn't directly parallel but instead staggered roughly front heel alongside his chums rear.
If one comes off when parallel he'll gather up his chum, as any peloton pile up demonstrates. This outcome is almost inevitable.
But when staggered the outside rider will have visual warning if the inner rider starts to go, and if the outside rider takes a spill the inner rider will likely be clear before matey hits the tarmac. Don't listen to the Mickey Mouse amateur bullpois BC trot out.