Yes, it's true, if the ignition of exhaust gasses is timed properly, it can keep the Turbo spinning, but you need to remember, a Turbocharger is not an internal combustion engine, it's meant to compress air and shove it down the Intake
, not withstand explosions in the exhaust housing. you will eventually break the turbine, especially if it's running hot when it occurs.
Race cars can get away with it, they aren't daily drivers, and stuff breaks on racecars all the time, most people don't tear-down and rebuild their daily drivers on a daily basis.
You ever see a show called "Junkyard Wars"?
There was an episode where the challenge was for the teams to build a jetcar, and race it.
One team built a pulse jet engine from surplus, it was reliable, and worked pretty good. the other team, on the other hand, opted to build a Turbo-jet powered car. They used a larger, automotive Turbocharger as the core of their engine. A Turbo Jet operates on a similar principle to the misfire system, only air/fuel mixture is burnt and the resulting reaction is forced through a turbine to create thrust (sound familiar?) Well guess what... The Turbocharger eventually suffered a major meltdown, the turbine blades shattered and needless to say, they lost the race (also of note, they thought it would hold up to the heat and stress... it didn't.)
There's a reason most racing organizations don't allow this method for reducing Turbo-lag. it's tricky, loud as hell, not to mention dangerous!