the reason we did it, was if you have ever driven an old HGV with a "crash " gear box , The blip of the throttle. A. brings up engine speed with the gear box speed Thus negating the shift! road speed can alter this so if you get it all syncronized you can actualy down shift without using the clutch!!!!
not sure what the proper reason for it is, but i do it to stop the back wheel working too hard against the engine. It can be good fun when you're playing about on the track getting the back to drift sideways into a corner but when I'm hard on the brakes in a straight line i'd rather not encourage the tyre to loose tractiona and waggle about!
Very tricky going down the box without the clutch... something i don't care to get to grips with, it just seems a bit abbusive!
When I go Clutch in, Blip, gear down, its so smooth but "Twist of the Wrist" says the bit about engine speed and recomends Clutch in, gear down, blip, clutch out......when I do this it no so smooth.