The British method I am referring to above is shot with the rifle butt in contact with the shoulder, not lowered, with your two-step bolt manipulation. The bolt knob is actually not ever released as the trigger is pulled with the middle finger as soon as the bolt is in battery. At top speed the accuracy I've seen produced is not comparable to your competition shooting, but watching a guy do it that knows how sheds light on why some old "Colonel Blimps" resisted the development of the semiauto rifle in the British Army, thinking it unnecessary.

As for reaching over the top left-handed with a righthanded rifle, the use of iron sights makes it much easier, obviously and typical hunting rifles with scopes mounted require the rifle be rotated to the left to open up the space allowable to get at the bolt, making it very hard {depending on the actual scope/bolt handle layout} to do with some rifles. Scoped rifles can be shot with the butt remaining on the left shoulder but it does require a great deal of practice.

As for your southpaw, what you are describing is very impressive shooting, and any Righty that disagrees with you should have a go at shooting a left-handed bolt rifle fast sometime for proof otherwise!!

almost forgot...

I just saw a hunting video last week where Craig Boddington fired a followup shot into a buff, just stopping his run to get the shot off. He reloaded pretty quickly, using his support hand to work the bolt, dropping the rifle to operate the bolt. I am curious as to whether he routinely uses his support hand to work the bolt, or whether he usually just reacheds over the top and used his support hand merely as a result of stress in the moment or because the rifle was scoped.