The TG Aus bit was filmed well ages ago - our version of the episode aired on September 28th. I'd say that's neither old nor new Stig, but Rally Stig what was brung on for the occasion. As for whomsoever is teaching the stars, clearly some good tutelage is happening - Bishop and Becker put some great laps in. Kinda like when Tiff tutored Boyle... Hmmmmm.... - [Eagle eyed pedants will note they shafted Boyle as to where they placed him on the board].
Seems guests with a B surname are fantabulous drivers, there's no other conclusion to be drawn.