I have seen groups of cyclists about that big on a road without closing the road down formally. Frequently on smaller roads that won’t have passing lanes, and even be double yellow. When caught behind them, I eagerly await the road widening and they pretty much always stick to the right lane and you can pass them at a courteus speed.
How is this “clearly” a race? This video shows no road closures or signage or any kind of race officials.
Groups like that don’t form randomly, unless it’s an event.
There’s also a person on a motorbike (an official, support, or a camera-man), usually seen in races.
I have seen groups of cyclists about that big on a road without closing the road down formally. Frequently on smaller roads that won’t have passing lanes, and even be double yellow. When caught behind them, I eagerly await the road widening and they pretty much always stick to the right lane and you can pass them at a courteus speed.