Its more of an issue with organic pads. Bedding in does 3 things – it cures the pad under heat and pressure, it conforms the pad to the disc and it deposits a microscopic layer of pad material on the disc.
This allows adherent friction to occur which is when you get a semimolten boundary layer that in effect sheers. thus you get long pad life. If you do not have this boundary layer you get abrasive friction and short pad life.
On the tandem the brakes get very hot indeed and are used a lot – and pads last thousands of miles not matter the conditions.
So brakes, riding styles, pads will bed in easily in normal riding, some rtequire the deliberate bedding in. You can tell the change in feel as they bed in. At the puffer I bedded in anew set of pads simply by dragging them down the main descent