I think it’s literally just dirt bikes with soldiers on them. If that video from a while back is any indication, they’re a lot like clay pigeon target practice for Ukraine’s drones.
It was a brilliant tactic in WW2 where most reconnaissance was done by pilots looking out their windows and noting what they saw.
In the days of computer analysis of satellite images, drone footage and just basic tools like heat-sensing IR cameras and Lidar, it’s not all that great an idea. It’s pretty easy to figure out just from heat signatures whether or not that line of tanks has no people in them.