One thing easily overlooked in that article, KarenH, is the numbers of drivers involved :

Devon and Cornwall Police said it had stopped the convoys on the A30 and M5 and prosecuted the two lead drivers of both convoys for careless and inconsiderate driving.

or again

he Nottinghamshire Brexit go slow protest along the M1 this evening - eight vehicles took part flanked by police cars

We all know how a single breakdown on a motorway can lead to very long tailbacks. So while the disruption may be very significant for any such action, it only takes a handful of people to cause it. Yet, because of the way media works, it is likely to get as much attention as today's march with hundreds of thousands of attendees.