OK, fair play.
First off, they're riding too close much of the time. The old adage "drive at a distance which will allow you to stop in the distance you can see to be clear" is as valid a mantra for cyclists as it is for motorists. If one comes off, everyone behind them will get gathered up and on a live carriageway that could have deadly consequences. About two bike lengths is optimimum - far enough to give following riders reaction time and space, close enough that overtaking drivers are discouraged from inappropriately darting in. This has secondary benefits, as we will see in a moment.
Also don't ride directly parallel. If one rider comes off they will gather their neighbour - any peloton crash video shows how that goes down. The outside rider can stay outside by all means but should stagger back slightly so their front axle is roughly level with the rear axle of the inside rider. While this is oft regarded as bad manners it does bring benefits, which are two-fold: if the inside rider starts to go wobbly the outside rider will have the visual cues to take evasive action, which they would be deprived of if directly parallel. If the outside rider drops it then the inside rider is likely going to be unaffected by virtue of already being 75% clear and trafelling away from danger.
Secondly, in the event that the group needs to drop from taking the full lane and into single file it should be the outside rider dropping to line, and in a staggered position they are better placed to do so. This allows less close manoeuvring, which = less chance to mess it up and come off. It also allows the move to be executed more quickly - youll be wanting to drop into line for a reason, so the quicker you do the safer you are.
In addition, if the following riders are two bike lengths behind, as per the first paragraph, then the space exists to enable to so instantly. As it stands when a typical group drops into single file its usually an undisciplined, dangerous shambles.
So nothing major, the boys all look like their control skills are decent enough, they just need to practice their positioning and drills for safe group riding. The road is a deadly place to have a peloton style pile up so it isn't wise to blithely emulate that positioning while training or even on a leisure ride. Staggered and spaced is the mantra.
It is a little ironic that a video intending to proppmote driver safety around cyclists features riders travelling in a less than safe manner themselves.
at least a regular tubed clincher has very good chance of being repaired at the roadside.
