The "finger spinny" stuff is very bad to do in a fighting context. When I started learning staff waaaay at the beginning of my journey through the martial arts, I used to play with the finger spinny stuff, 'cuz it looked cool. my teacher yelled at me a lot for this, so I had to work very hard to break myself of that habit. Now I have to work twice as hard to get it back.
The reason it's bad to do, in case you're wondering, is that if the staff get's hit in the wrong point of the spin you can break your fingers and do all sorts of weird muscle damage. Fingers break quite easily, and staffs have a lot of leverage and a lot of torque for such small muscles.
In a strictly fire context, I don't see how there is much harm in it. In fact it looks pretty cool. But maybe the fighting thing is where the rumor you heard came from.
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If you love something, set it on fire.