No, the burden of proof is on you. The theory of the circumpolars is not complete yet, but at the moment its the only one that accounts for all of the evidence in some sort of way. If you disagree that the shaft was for that purpose, then you have to provide some sort of convincing alternative explanation for why they would have gone to all that effort.

Occam's razor says the simplest explanation that takes in all the evidence is the one that should be used. Your refusal to accept it is not an explanation, so its up to you to convince otherwise.

Dave L