Sports bikes in particular don't have much steering angle to work with, so at slow speeds - on a course designed to test slow speed manouvering - they can have wide turning circles.

It is possible to turn more tightly but it requires leaning much more into the turn. That needs a lot of skill and confidence to do smoothly at low speed when the bike has a high center of gravity. The bike will crash if you brake or stall, and on a sports bike there often isn't a huge amount of torque at low engine speeds, so you need to be very adept at clutch slipping and modulating the rear brake.

The course in the video isn't that bad though. A U-turn on the road, a mandatory part of the UK test, is done with a tighter radius than anything on that video.