isn't that a contradiction?
Depends on the person and type of spinner.
Not all yoyos have ball bearings. Skateboards predate inline skates IINM.
Fidgets helping people stay focused is highly debatable, might even have diametrically opposite effect!
Skateboarding goes in and out as hobby. Was pretty popular a few years ago.
Real yoyos have bearings. The rest are cheap junk that don't even spin.
Whether or not spinners help people stay focused or release anxiety doesn't really matter, because people believe it helps.
So unless studies come out convincing people otherwise, they will continue to use them for that purpose.