Yeah, once I thinked a bit about it and I had the same conclusion (there is more than one Stig)There is more than One Stig.For Top Gear followers: once they said The Stig was Schumacher.
I guess we all know that is a big lie, but anyway...
Once, Schumacher was one.
They are probably that special drivers that do the racing parts in movies like Fast and Furious or Death Race. The fact of Top Gear use a misterious character instead of a lot of pilots is just a marketing idea.
But if Schumacher was once the Stig? Only in that TV episode. They would win much more money making a episode where Schumacher was driving beeing Schumacher than dressing Schumacher with the Stig clothes.