Perhaps the officers got confused in the briefing. Picnic & Nitpick do sound similar . 
It appears to be an all too familiar scene with the police...in short the two ladies were easy targets. The police, as with litter wardens, know their limitations. It's easier to prosecute a mum because her small child has accidentally dropped a sweet wrapper out of the pushchair without her knowledge than to prosecute a couple of yobbo's swearing and dropping fast food wrappers everywhere.
The police have been given powers during this pandemic but don't use much common sense when enforcing it. Instead of say riding the buses STOPPING people who haven't a mask from boarding {as it plainly says on the front of most buses}, stopping them going into shops for the same reason, they would sooner drive out into the "less" populated countryside in their nice comfy motors and pick on descent citizens.
One thing these ladies should have done is ask the policemen concerned if they were doing the same....I.E. they were "Derbyshire Police" which means they could have arrived at that location from as much as 20 miles away, they obviously had to "walk" to approach the ladies, a pound to a penny says their police car contained refreshment of some kind {sandwiches...soft drinks....coffee...sweets}.