I can’t say for certain without seeing the video and knowing the actual situation, but usually “hit and run” refers to detectorists that have a set time limit in mind when they detect a new site - if they aren’t getting any significant or valuable finds within, say, fifteen minutes or half an hour, they pack up and move on to the next site. The philosophy is that if the site isn’t producing anything good within that time, then there isn’t enough there to make spending any more time worthwhile. Kind of an extreme version of “cherry picking” for some - for others, they just get bored if they aren’t finding good targets every few minutes. To me, it’s one of many reasons why I can still go into just about any location and still find good finds if I’m willing to be patient and persevere - I’d rather be detecting than constantly driving to the next site. But as always, different strokes for different folks. A hit and run advocate would tell me I’m wasting time on sites that don’t produce enough.
Anyways, no, the video you were watching most likely wasn’t advocating anything nefarious, like hunting quickly in an area where they know they shouldn’t be (trespassing, etc) and bugging out before getting caught. Although that surely happens, it wouldn’t be wise to post videos of yourself doing it!